I-76: Implemented Email Notification System for Different User Interaction scenarios. (E-01-S04)

[Shahed-Chy-Suzan]

Fixes #76

• [x] Does not depend on other PRs
• [ ] Depends on other PR being merged first: #

What kind of change does this PR introduce (check at least one)

• [ ] Bugfix
• [ ] Improvement
• [x] New feature
• [ ] Refactor
• [x] Infrastructure
• [ ] Other (please specify)

How would you describe the changes in a changelog (1-2 lines)?

Added email notification system using AWS SES for user registration with welcome email functionality, and implemented infrastructure for future email notification scenarios.

Related Issues/PRs (optional)

• Sending OTP and Forget Password mail is done by cognito in PR #113

How to test

1. Register a new user in the system
2. Verify welcome email is received after successful registration
3. Check email content matches the defined template
4. Verify email is sent from correct sender address (no-reply@bloodconnect.net)
5. Verify AWS SES domain verification is working

• [x] Needs regression testing (add QA needed label)

Checklist

• [x] I have tested these changes locally and they function as expected.
• [ ] I have added or updated necessary documentation to reflect the changes.
• [x] I have followed the project's coding style and guidelines.
• [x] I have added appropriate test coverage to ensure the changes are functioning correctly.
• [x] I have checked for any potential conflicts with other branches or pull requests.
• [ ] I have updated necessary OpenAPI specs

Deploy risk & follow up

• [x] No risk
• [ ] Low
• [ ] High