[API-39223] Update poa docs to include dependent claimants

[tycol7]

⚠️ Do not merge until after release

Summary

• Add new Appointing an accredited representative for dependents section under Background for v1 and v2.
• Update endpoint descriptions:
  • v1 POST /forms/2122
  • v2 POST /veterans/{veteranId}/2122
  • v2 POST /veterans/{veteranId}/2122a

Related issue(s)

API-39223

Testing done

• New code is covered by unit tests
• Visual inspection

Screenshots

New section (v1)

New section (v2)

POST /2122 (v1)

POST /2122 (v2)

POST /2122a (v2)

What areas of the site does it impact?

v1 and v2 docs

Acceptance criteria

• I updated 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 (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

Requested Feedback

N/A