Return suitable status on an invalid request

Purpose/Overview:
We need to improve the validation of the request body. And return a suitable status

Technical approach:

• Add unit tests
• Add exceptions to handler

TODO:

• Add KARATE tests

POST request to "/password/validate"

Scenario 1:
When body is empty 
   Expected result: status 400 Bad request
   Actual result: status 500 Internal Server Error

Scenario 2:
When userId is incorrect or not provided
   Expected result: status 422 Unprocessable Entity
   Actual result: status 500 Internal Server Error

Scenario 3:
When password is not provided
   Expected result: status 422 Unprocessable Entity
   Actual result: status 500 Internal Server Error