[SELC-4929] refactor: Replace Notification Manager with AWS SDK

[manuraf]

List of Changes

• Integrated AWS SDK for sending emails, replacing the existing mechanism that relied on the notification-manager microservice.
• Adjusted configuration and environment settings to support AWS SDK integration.

Motivation and Context

This pull request introduces two major changes aimed at optimizing the onboarding process and deprecating the notification-manager microservice:

1. Removal of Unused Variables:

Cleaned up the codebase by eliminating variables that are no longer used in the onboarding process. This helps in reducing clutter and potential confusion in the code.

2. Replacement of Email Sending Functionality:

Replaced the email sending functionality previously handled by the notification-manager microservice with AWS SDK.
This change is part of our effort to phase out the notification-manager microservice and streamline our notification system.

How Has This Been Tested?

Screenshots (if appropriate):

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[sonarqubecloud]

Quality Gate passed

Issues
8 New issues
0 Accepted issues

Measures
0 Security Hotspots
95.7% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud