Issue:
feat(connector): add support for affirm and afterpay/clearpay through stripe

### Feature Description

Add support for creating payments through affirm and afterpay/clearpay through stripe. The api contract changes will be as follows
- afterpay/clearpay
```json
{
  "payment_method": "pay_later",
  "payment_method_data": {
    "issuer_name": "afterpay_clearpay",
    "afterpay_clearpay_redirect": {
      "billing_email_address": "abc@gmail.com"
    }
  }
}
```
- affirm
```json
{
  "payment_method": "pay_later",
  "payment_method_data": {
    "issuer_name": "affirm",
    "affirm_redirect": {
      "billing_email_address": "abc@gmail.com"
    }
  }
}
```

### Possible Implementation

Modify the payments request of stripe to include affirm and afterpay

### Have you spent some time to check if this feature request has been raised before?

- [X] I checked and didn't find similar issue

### Have you read the Contributing Guidelines?

- [X] I have read the [Contributing Guidelines](https://github.com/juspay/hyperswitch/blob/main/contrib/CONTRIBUTING.md)

### Are you willing to submit a PR?

Yes I am willing to submit a PR!

- [X] Support for affirm #355 
- [ ] Support for afterpay_clearpay

Resolution:
<think>
PR Context:
- Title: feat(connector): add support for affirm through stripe
- Merged: 2023-01-12T12:00:22Z
- Files changed: 3 files
- Commits: 5 commits

Implementation approach:
## Type of Change
<!-- Put an `x` in the boxes that apply -->

- [x] New feature

## Description
<!-- Describe your changes in detail -->
This pr will add support for making affirm payments through stripe.
Few code enhancements that I have included in this PR
- change stripe payment method types from `String` to `StripePaymentMethodType`.
- make changes to  `StripePayLaterData` so that it is usable for all pay later payments ( klarna, affirm, afterpay_clearpay )


## Motivation and 
</think>

To implement this, you'll need to modify:


**Detailed Implementation:**


**Commit 1:** feat(connector): add support for affirm through stripe (#355)
Files to modify:


**crates/api_models/src/payments.rs**
  Modify existing code

**crates/router/src/connector/stripe/transformers.rs**
  Remove:
    - struct: pub::StripeKlarnaData
  Add:
    - struct: pub::StripePayLaterData

**crates/router/src/core/payment_methods/transformers.rs**
  Modify existing code