[Testing] New subscription workflow using Orders API

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### Problem

https://gitlab.com/gitlab-org/customers-gitlab-com/-/issues/4319 created FF `use_orders_api_subscription_workflow`, when enabled will use the Orders API for new subscription (except for marketplace and in preview mode).

This issue is to track the testing progress before the go-live of this functionality.

Part of [Orders API upgrade epic](https://gitlab.com/groups/gitlab-org/-/epics/6438).

### Testing scenarios

<!-- Consult with `@gitlab-com/business-technology/enterprise-apps/zuora-architects` on the ~"Enterprise Applications" team if Zuora business logic is involved. -->

|Scenario|Steps|Expected result|Pass? (Staging environment)|Notes|
|---|---|---|---|---|
|Create a new SAAS subscription for a new customer from gitlab.com|1. Create new user in gitlab.com <br /> 2. Create a group<br />3. Navigate to billings page<br />4. Select a plan and fill billing details <br /> 5. Purchase subscription <br />|Customer, Order and Subscription is created with appropriate attributes| :white_check_mark: [Verification link](https://drive.google.com/file/d/1CzBtMrDXiMe3XeTNrxmIyeEbRHwDEkWi/view?usp=sharing) <br> :white_check_mark: [automated test](https://gitlab.com/gitlab-org/gitlab/-/quality/test_cases/347667) | `vat_id` is not set for new customer: [Issue](https://gitlab.com/gitlab-org/customers-gitlab-com/-/issues/4584), [MR](https://gitlab.com/gitlab-org/customers-gitlab-com/-/merge_requests/5143): [fixed](https://gitlab.com/gitlab-org/customers-gitlab-com/-/issues/4584#note_1046761737) |
|Create a new SAAS subscription for a new customer from CDot|1. Create a new user new user in gitlab.com <br /> 2. Sign in CDot via gitlab.com <br />3. Select 'Buy a new subscription' <br /> 4. Enter plan and billing details <br /> 5. Purchase subscription|Customer, Order and Subscription is created with appropriate attributes| :white_check_mark: [Verification link](https://drive.google.com/file/d/1W1K5cQ5Xc05V3uj-XJr-qAXwj4U6T-Ca/view?usp=sharing)<br> :white_check_mark: [automated test](https://gitlab.com/gitlab-org/customers-gitlab-com/-/quality/test_cases/2749)||
|Create a new SAAS subscription for an existing customer from gitlab.com|1. Sign in to an existing user in gitlab.com <br /> 2. Create a group<br />3. Navigate to billings page<br />4. Select a plan and fill billing details <br /> 5. Purchase subscription <br />|Order and Subscription is created with appropriate attributes| :white_check_mark: [Verification link](https://drive.google.com/file/d/1BMfZkI0t7PPUICtLWZceqLN1mVjuvxi5/view?usp=sharing) <br> :white_check_mark: [automated test](https://gitlab.com/gitlab-org/gitlab/-/quality/test_cases/349085)||
|Create a new SAAS subscription for an existing customer from CDot|1. Sign in to an existing user in CDot <br />2. Select 'Buy a new subscription' <br /> 3. Enter plan and billing details <br /> 4. Purchase subscription |Order and Subscription is created with appropriate attributes| :white_check_mark: [Verification link](https://drive.google.com/file/d/1oy6TZkd41TWc7VrBl7Fc3RdT-RkK8LR7/view?usp=sharing)<br> :white_check_mark: [automated test](https://gitlab.com/gitlab-org/customers-gitlab-com/-/quality/test_cases/2752)||
|Create a new self managed subscription for a new customer from CDot|1. Sign up CDot <br />2. In billing page, select option to buy 'self-managed' subscription' <br /> 3. Enter active user count and billing details <br /> 4. Purchase subscription | Order and Subscription is created with appropriate attributes. Activation code is emailed to user | :white_check_mark: [Verification link](https://drive.google.com/file/d/15uSeIB693OuqvzcKoNTmfkhFVqlnL_mR/view?usp=sharing) <br> :white_check_mark: [automated test](https://gitlab.com/gitlab-org/customers-gitlab-com/-/quality/test_cases/3096)||
|Create a new self managed subscription for an existing customer from CDot|1. Sign in to an existing user in CDot <br />2. In billing page, select option to buy 'self-managed' subscription' <br /> 3. Enter active user count and billing details <br /> 4. Purchase subscription | Order and Subscription is created with appropriate attributes. Activation code is emailed to user | :white_check_mark: [Verification link](https://drive.google.com/file/d/1Qs0qAhmyrGRr2KESGZ3XzCxGP3jkyJbz/view?usp=sharing)<br> :white_check_mark: [automated test](https://gitlab.com/gitlab-org/gitlab/-/quality/test_cases/347667) ||
|Preview a subscription |1. Login to CDot <br /> 2. Visit url to create subscription with plan param ([http://localhost:5000/subscriptions/new?plan_id=2c92c0f97700a4f7017704c7fe465919 example](url)) <br /> 3. Enter purchase details | Request is directed to Subscribe API. Orders API is not used for preview | :white_check_mark: [Verification video](https://drive.google.com/file/d/14KZVb0unCTO36OO2cj0KVxOgbcUmM8tA/view?usp=sharing)<br> :white_check_mark: [automated test](https://gitlab.com/gitlab-org/customers-gitlab-com/-/quality/test_cases/3424) ||
|Create a new marketplace subscription for an existing customer| Follow the description in this [comment](https://gitlab.com/gitlab-org/customers-gitlab-com/-/issues/4562#note_1033256197) | Request is directed to Subscribe API. Orders API is not used for preview(Marketplace subscription does not use the preview) | :white_check_mark: [Verification video](https://drive.google.com/file/d/1DYJnjh8cGyewP1doGcjM7WtEuYCEXAL2/view?usp=sharing) |  |
|Create a new marketplace subscription for a new customer| Follow the description in this [comment](https://gitlab.com/gitlab-org/customers-gitlab-com/-/issues/4562#note_1033256197) | Request is directed to Subscribe API. Orders API is not used for preview(Marketplace subscription does not use the preview) | :white_check_mark: [Verification link](https://drive.google.com/file/d/1DryYncJvJ41yDpaLaHQCo115zswI5Cc_/view?usp=sharing) |  |
| Purchase additional CI minutes (new add-on subscription) | 1. Create a new user on gitlab.com <br/> 2. Create a group <br/> 3. Navigate to Usage Quotas -> Pipeline tab <br/> 4. Click on 'Buy additional minutes' <br/> 5. Fill in quantity and payment details. Submit form | New subscription is created for additional CI minutes purchase using Order's API. Reflects in gitlab.com | :white_check_mark: [Verification link](https://drive.google.com/file/d/1Ii_a7QWgFeZEZgMJmZIapZxH_bNnaSs6/view?usp=sharing) |  |
| Purchase additional storage (new add-on subscription) | 1. Create a new user on gitlab.com <br/> 2. Create a group <br/> 3. Navigate to Usage Quotas -> Storage tab <br/> 4. Click on 'Buy storage' <br/> 5. Fill in quantity and payment details. Submit form | New subscription is created for additional storage purchase using Order's API. Reflects in gitlab.com | :white_check_mark: [Verification link](https://drive.google.com/file/d/1HUDdEXxihEOETEsdRU41QT9fFbW7QufC/view?usp=sharing) |  |
| New OSS SaaS subscription | 1. Generate coupon (refer doc/coupon.md) <br/> 2. Create a new group gitlab.com <br/> 3. Sign in CDot via gitlab.com <br/> 4. Navigate to [Community Program Page for OSS](https://customers.staging.gitlab.com/subscriptions/community_program/new?product=oss) and select `Claim SaaS` <br/> 5. Select group <br/> 6. Enter quantity and coupon details <br/> 7. Purchase subscription  | New subscription is created using Order's API for the quantity specified. Reflects in gitlab.com. Amount is 0. | :white_check_mark: [Verification link](https://drive.google.com/file/d/1uE24F8Q_iLkz_zudLBs9o44od0p7gsQW/view?usp=sharing) |  |
| New EDU SaaS subscription | 1. Generate coupon (refer doc/coupon.md) <br/> 2. Create a new group gitlab.com <br/> 3. Sign in CDot via gitlab.com <br/> 4. Navigate to [Community Program Page for EDU](https://customers.staging.gitlab.com/subscriptions/community_program/new?product=edu) and select `Claim SaaS`  <br/> 5. Select group <br/> 6. Enter quantity and coupon details <br/> 7. Purchase subscription  | New subscription is created using Order's API for the quantity specified. Reflects in gitlab.com. Amount is 0. | :white_check_mark: [Verification link](https://drive.google.com/file/d/103DnUBkOO5wfByI9kAW796KuM8__qlEO/view?usp=sharing) |  |
| New OSS self managed subscription | 1. Generate coupon (refer doc/coupon.md) <br/> 2. Sign in CDot <br/> 3. Navigate to [Community Program Page for OSS](https://customers.staging.gitlab.com/subscriptions/community_program/new?product=oss) and select `Claim self-managed` <br/> 4. Enter number of seats <br/> 5. Enter coupon code <br/> 6. Purchase subscription  | New subscription is created using Order's API for the quantity specified. Amount is 0. | :white_check_mark: [Verification link](https://drive.google.com/file/d/1Ec95P7F6PeSdcNezEFtfwtL_v8dCKITZ/view?usp=sharing) |  |
| New EDU self managed subscription | 1. Generate coupon (refer doc/coupon.md) <br/> 2. Sign in CDot <br/> 3. Navigate to [Community Program Page for EDU](https://customers.staging.gitlab.com/subscriptions/community_program/new?product=edu) <br/> 4. Enter number of seats <br/> 5. Enter coupon code and select `Claim self-managed` <br/> 6. Purchase subscription  | New subscription is created using Order's API for the quantity specified. Amount is 0. | :white_check_mark: [Verification link](https://drive.google.com/file/d/10Z9LGbw2krfXxbrUxyDZEfRuFPsIwQB_/view?usp=sharing) |  |
| Amend an existing subscription by purchasing new seats | 1. Create a group <br/> 2. Upgrade the group to a paid plan <br/> 3. Update seat quantity  | Verify amendment API is used. <br/> Seat quantity is updated <br/> Reflects in gitlab.com, CDot | :white_check_mark: [Verification link](https://drive.google.com/file/d/1opWVVtPxiGvtAxh7crPhWbZem-qxOjW0/view?usp=sharing) |  |
| Amend an existing subscription by purchasing additional minutes | 1. Create a group and a project within the group. Verify shared runners is enabled (`Settings` -> `CI/CD` -> `Runners`) <br/> 2. Upgrade the group to a paid plan <br/> 3. Navigate to `Settings` -> `Usage Quota` (Pipelines tab). <br/> 4. Click 'Buy additional minutes' <br/> 5. Fill in quantity and payment details. Submit. | Verify Amendment API is used to purchase additional minutes. <br/> Additional CI minutes purchased is reflected in gitlab.com, CDot and Zuora | :white_check_mark: [Verification link](https://drive.google.com/file/d/1sBfZNIrZkG05MdnSeKbcugqoxzwtifZj/view?usp=sharing) |  |

### Result

### Next steps (if any)

### How will we measure success?

Story points: 2.0