Allow the User to Change Ratings & Reviews for any particular book

**Current Behavior:**
The Portal doesn't allow one to modify the ratings & reviews already made. Currently due to Exception Handling, the `SQLIntegrityConstraintViolationException` is handled gracefully.

**Required Behavior:**
Subscriber Must be allowed to modify or edit the Ratings & Reviews

**Important Info:**
The Servlet file: `WEB-INF/classes/reviewSubmitServlet.java` handles this functionality & need modifications.

Start with WEB-INF/classes/reviewSubmitServlet.java and trace how an existing rating or review reaches SQLIntegrityConstraintViolationException. Confirm the current database behavior for a subscriber submitting another review for the same book. Done means the subscriber can modify that rating or review without the exception being the only handled outcome.

Written by the indexing model from the issue text.