Refactor: simplify eligibility verification forms

[thekaveman]

Closes #3396

• Moves __init__ kwargs to class attribute for easier inheritance
• Moves default attribute values into base class where appropriate to reduce duplication
• Adds server-side validation (not strictly necessary, since we also do HTML client-side validation)
• Refactors tests to be class-based, check valid and invalid data states

Reviewing

To get setup, start with the fixtures file in LastPass for Littlepay, and add the following entries:

{
  "model": "core.transitagency",
  "pk": 2,
  "fields": {
    "active": true,
    "slug": "mst",
    "short_name": "MST (local)",
    "long_name": "MST (local)",
    "info_url": "https://www.agency-website.com",
    "phone": "1-800-555-5555",
    "eligibility_api_config": 1,
    "logo": "agencies/cst.png"
  }
},
{
  "model": "core.transitagency",
  "pk": 3,
  "fields": {
    "active": true,
    "slug": "sbmtd",
    "short_name": "SBMTD (local)",
    "long_name": "SBMTD (local)",
    "info_url": "https://www.agency-website.com",
    "phone": "1-800-555-5555",
    "eligibility_api_config": 1,
    "logo": "agencies/cst.png"
  }
},
{
  "model": "core.eligibilityapiverificationrequest",
  "pk": 2,
  "fields": {
    "label": "courtesy_card",
    "api_url": "http://server:8000/verify",
    "api_auth_header": "X-Server-API-Key",
    "api_auth_key_secret_name": "agency-card-flow-api-auth-key",
    "api_public_key": 1,
    "api_jwe_cek_enc": "A256CBC-HS512",
    "api_jwe_encryption_alg": "RSA-OAEP",
    "api_jws_signing_alg": "RS256"
  }
},
{
  "model": "core.eligibilityapiverificationrequest",
  "pk": 3,
  "fields": {
    "label": "mobility_pass",
    "api_url": "http://server:8000/verify",
    "api_auth_header": "X-Server-API-Key",
    "api_auth_key_secret_name": "agency-card-flow-api-auth-key",
    "api_public_key": 1,
    "api_jwe_cek_enc": "A256CBC-HS512",
    "api_jwe_encryption_alg": "RSA-OAEP",
    "api_jws_signing_alg": "RS256"
  }
},
{
  "model": "core.enrollmentflow",
  "pk": 6,
  "fields": {
    "system_name": "courtesy_card",
    "label": "Courtesy Cardholder",
    "display_order": 6,
    "api_request": 2,
    "supported_enrollment_methods": ["digital"],
    "transit_agency": 2
  }
},
{
  "model": "core.enrollmentflow",
  "pk": 7,
  "fields": {
    "system_name": "mobility_pass",
    "label": "Mobility Pass Cardholder",
    "display_order": 7,
    "api_request": 3,
    "supported_enrollment_methods": ["digital"],
    "transit_agency": 3
  }
},

Then for each of CST, MST, and SBMTD, confirm:

1. The agency card option displays on the /eligibility page
2. Selecting the agency card option displays the agency-specific language on the /eligibility/start page
3. Continuing to the /eligibility/confirm page shows the agency-specific form/language
4. Submit the CST form with valid sample data, see the eligibility confirmation page / enrollment index
5. Submit MST and SBMTD with any sample data, see the ineligible page

[github-actions]

Coverage report

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
benefits/core
widgets.py
benefits/eligibility
forms.py
Project Total

This report was generated by python-coverage-comment-action

[lalver1]

This is a nice cleanup, it looks good to me! I also tested locally and saw no issues.

While going over the new class attributes I did notice that originally name_placeholder for CST was Hernandez-Demarcos but in this PR it becomes Garcia due to the default value of the attribute. This doesn't affect anything though so we're good 👍

[thekaveman]

@angela-tran I saw your 👀 on the PR description -- just checking if you wanted to review before I merge?

[angela-tran]

@angela-tran I saw your 👀 on the PR description -- just checking if you wanted to review before I merge?

That's ok, you can go ahead with merging. I've skimmed through most of the changes and didn't have any pending thoughts or anything. Thanks for checking!