Api 24720 validation consolidation

[mchristiansonVA]

Summary

• Refactored logic in controller and validator classes such that the same validation is applied for calls to /validate and /intent-to-file endpoints.

Related issue(s)

API-24720

Testing done

• Tested with Postman to confirm the same validation is applied for calls to /validate and /intent-to-file.
• Tested with Postman to confirm all ITF endpoints are working as expected, and calls passing validation are successful.
• Added a new rspec test to confirm valid SSN parameter with hyphens is correctly handled.

What areas of the site does it impact?

• Vets.api Benefits Claims ITF endpoints.

Acceptance criteria

• I fixed|updated|added unit tests and integration tests for each feature (if applicable).
• No error nor warning in the console.
• Events are being sent to the appropriate logging solution
• Documentation has been updated (link to documentation)
• No sensitive information (i.e. PII/credentials/internal URLs/etc.) is captured in logging, hardcoded, or specs
• Feature/bug has a monitor built into Datadog or Grafana (if applicable)
• If app impacted requires authentication, did you login to a local build and verify all authenticated routes work as expected
• I added a screenshot of the developed feature