Implement Pre-Fill Functionality in vets-api for Forms 21-22 & 21-22a

[oddball-lindsay]

Background

As part of our Appoint a Rep MVP, we would like to make use of the form pre-fill functionality. Research to implement this functionality was done in #66168 with the following findings:

Form pre-fill for the vets-api backend is thoroughly explained here: https://github.com/department-of-veterans-affairs/va.gov-team/blob/master/teams/vsa/teams/ebenefits/engineering/prefill_setup.md. An example PR that runs through all the necessary additions is here: department-of-veterans-affairs/vets-api#5391.

Open Questions

1. Are our form URLs already determined?
2. Do we already have form names that map to our form numbers like vre_readiness: ['28-1900']?

Tasks

• Check in with the team to identify answers to the questions above
• Two prefill classes, one each for 21-22 and 21-22a. These prefill classes need a metadata method that includes that we want to enable prefill, a version, and a return URL. The return URL is the first page of the form. Example: https://github.com/department-of-veterans-affairs/vets-api/blob/master/app/models/form_profiles/va_0993.rb.
• Two form profile mappings that define what fields we want prefilled and where that data comes from. Example: config/form_profile_mappings/28-1900.yml.
• Add the two forms to app/models/form_profile.rb. They need to be defined under ALL_FORMS and FORM_ID_TO_CLASS.
• Add a definition of our form with prefill: true to config/settings.yml
• Add two tests to spec/models/form_profile_spec.rb to cover each form

Acceptance Criteria

• Pre-fill has been implemented in vets-api for our Appoint a Representative product, so that authenticated users do not have to enter any information that already exists in their VA Profile.

[cosu419]

8/8 update: two outstanding PRs that must merge in sequence. The first has been approved but checks are timing out. Once those pass, the second will need to be re-reviewed.