VSN-2373 : Adding feature of user uuid retrieval by user email.

Merge Request Description

feat: Adding method signature

This commit introduces the initial method signature required for retrieving a user UUID by their email. It establishes the foundation of the feature by defining the contract that subsequent implementations will follow.

feat: Defining implementation

This commit provides the concrete implementation of the previously defined method signature. It ensures that the logic for retrieving a user UUID by email is properly handled within the service layer.

feat: Exposing feature via controller

This commit exposes the implemented functionality through the controller layer. By doing so, the feature becomes accessible via API endpoints, allowing external services or clients to retrieve a user UUID using an email address.

docs: changelog update

This commit updates the project documentation, specifically the changelog, to reflect the addition of the new feature. It ensures that contributors and users are informed about the changes introduced in this merge request.

Closes VSN-2373