fix: Handle null SemanticModelStatus with 400 Bad Request in save and update APIs

[mittalVaghela]

Description

This PR for save and update api to properly handle cases where the SemanticModelStatus parameter is null. Instead of resulting in an internal server error (HTTP 500), the application now returns a 400 Bad Request with a descriptive error message.

Fix

• Error Handling: Updated the logic to check for null values in the SemanticModelStatus parameter for both save and
  updateModel methods.
• Response Update: Modified the API response to return a 400 Bad Request status when SemanticModelStatus is null, instead of a 500 Internal Server Error.
• Error Message: Provided a clear and informative error message: "SemanticModelStatus cannot be null. Valid values are: DRAFT, RELEASED, STANDARDIZED, DEPRECATED."

Issue:

Fixes #289

Pre-review checks

Please ensure to do as many of the following checks as possible, before asking for committer review:

• DEPENDENCIES are up-to-date. Dash license tool. Committers can open IP issues for restricted libs.
• Copyright and license header are present on all affected files

[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

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

See analysis details on SonarCloud