Refactor: move IdG config to EligibilityVerifier

[lalver1]

Closes #2237

Testing locally

1. Checkout the main branch
2. Make sure that your local_fixtures.json (or whatever fixture you are using) has a ClaimsProvider and an EligiblityVerifier that has a foreign key reference to that claims provider.
3. Run bin/reset_db.sh (now your local DB mirrors the structure of the dev environment)
4. Checkout this PR's branch
5. Run bin/init.sh (running this PR's migration on top of existing DB structure)

• For all EligiblityVerifiers that have a ClaimsProvider, confirm that the data in EligiblityVerifier.claims_provider.scope and EligiblityVerifier.claims_provider.claim was migrated to EligiblityVerifier.claims_scope and EligiblityVerifier.claims_claim, respectively.
• Confirm that when the code calls anEligiblityVerifier.claims_scheme instance, the value of claims_scheme equals the value of the associated ClaimsProvider.scheme if claims_scheme is blank in the database. Otherwise, claims_scheme should equal the value set for EligiblityVerifier in the database.
• Flows using scopes/claims from IdG should still work
• In the admin panel, when not logged in as a super user, check that Claims scheme under a selected Eligibility verifiers is read-only.

Notes/Questions

• Is the setter method for claims_scheme

@claims_scheme.setter
def _set_claims_scheme(self, value):
    self._claims_scheme = value

actually needed? I included it because I thought that it would be required for setting the value using the admin interface, but I did some testing (with it removed) and it doesn't seem to be needed. We also don't set claims_scheme in the code, so maybe I should remove it?

[github-actions]

Coverage report

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
benefits/core
admin.py
models.py
benefits/eligibility
verify.py
benefits/oauth
client.py
views.py
Project Total

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

[github-actions]

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[angela-tran]

I think we can put this logic inline in uses_claims_verification and remove this method.

[lalver1]

I agree, removing this method made the model a bit simpler 👍

[thekaveman]

This is largely looking good 👍

I think the claims_scheme field needs a little more work though.

[thekaveman]

Getting closer

[thekaveman]

This LGTM! And I tested it locally with dev IdG and the older adults flow, worked ✔️