Issue:
Bug: [REFACTOR] Update URL's in welcome email



There is an issue with URL's in the welcome email.

- Slack invite link - Expired
- Quarterly roadmap link - pointing to old quarter.



Pull request description:
## Type of Change
<!-- Put an `x` in the boxes that apply -->

- [ ] Bugfix
- [ ] New feature
- [ ] Enhancement
- [x] Refactoring
- [ ] Dependency updates
- [ ] Documentation
- [ ] CI/CD

## Description
<!-- Describe your changes in detail -->

Updated quarterly roadmap and slack invite URL's in `welcome_to_community.html` file which is sent as the email body whenever a user signs up.

### Additional Changes

- [ ] This PR modifies the API contract
- [ ] This PR modifies the database schema
- [ ] This PR modifies application configuration/environment variables

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1. `config`
2. `crates/router/src/configs`
3. `loadtest/config`
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## Motivation and Context
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## How did you test it?
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## Checklist
<!-- Put an `x` in the boxes that apply -->

- [ ] I formatted the code `cargo +nightly fmt --all`
- [ ] I addressed lints thrown by `cargo clippy`
- [ ] I reviewed the submitted code
- [ ] I added unit tests for my changes where possible


Testing:

Patch:
diff --git a/crates/router/src/services/email/assets/welcome_to_community.html b/crates/router/src/services/email/assets/welcome_to_community.html
index bb6c67a2624..f7e9b15b332 100644
--- a/crates/router/src/services/email/assets/welcome_to_community.html
+++ b/crates/router/src/services/email/assets/welcome_to_community.html
@@ -46,9 +46,9 @@
         >.
       </p>
       <p>
-        We’ve got an exciting Q2 roadmap ahead — check it out here:
-        <a href="https://docs.hyperswitch.io/about-hyperswitch/roadmap-q2-2025"
-          >Roadmap Q2 2025</a
+        We’ve got an exciting roadmap ahead — check it out here:
+        <a href="https://docs.hyperswitch.io/about-hyperswitch/roadmap"
+          >Our quarterly roadmap</a
         >.
       </p>
       <p>
@@ -58,7 +58,7 @@
         >
         or our
         <a
-          href="https://join.slack.com/t/hyperswitch-io/shared_invite/zt-2jqxmpsbm-WXUENx022HjNEy~Ark7Orw"
+          href="https://inviter.co/hyperswitch-slack"
           >Slack Community</a
         >.
       </p>