99310-Implement-POA-Establishment-Method-In-Lighthouse-API-Client

[patrick-brown-oddball]

Summary

• Work this ticket - Implement POA Establishment Method In Lighthouse API Client va.gov-team#99310
• It adds an ability to submit a 2122 form to Lighthouse
• I couldn't figure out VCR. Once access comes through, I'll take some free time so I can finish the ticket fully
• *I used these docs from lighthouse as my guide - https://developer.va.gov/explore/api/benefits-claims/docs?version=current *

Related issue(s)

It is related to this ticket which I will work on and finish soon - department-of-veterans-affairs/va.gov-team#99465

Testing done

• New code is covered by unit tests
• Will work on VCR cassettes more later

Acceptance criteria

• Handle responses, including error responses, following the conventions of sibling endpoint methods