API-22649-new-526-endpoints

[stiehlrod]

Summary

• Adds the following endpoints for 526:
  post '/:veteranId/526', to: 'disability_compensation#submit'
  post '/:veteranId/526/validate', to: 'disability_compensation#validate'
  post '/:veteranId/526/attachments', to: 'disability_compensation#attachments'

Related issue(s)

• API-22649
• API-22650
• API-22651

Testing done

• Rspec

What areas of the site does it impact?

vets-api

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