Add keycloak support

[kernicPanel]

Purpose

Now that richie users could login with keycloak openid, we have to support the sent token.

[Copilot]

Pull request overview

This PR adds support for Keycloak-flavored OIDC/JWT tokens (different typ claim and user-identifying claim like preferred_username) so Joanie can correctly authenticate and synchronize users when Richie is configured with Keycloak.

Changes:

• Introduces a Keycloak-compatible JWT token class and makes SimpleJWT settings configurable for Keycloak (ISSUER, JWK_URL, TOKEN_TYPE_CLAIM, USER_ID_CLAIM).
• Centralizes username extraction from authenticated requests via a new get_authenticated_username helper and updates multiple endpoints/filters to use it.
• Extends the test suite (and perf expectations) to cover Keycloak token shapes and resulting user-sync queries.

Reviewed changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
src/backend/joanie/core/authentication.py	Adds Keycloak token class and tweaks token→user field extraction logic.
src/backend/joanie/core/utils/api.py	New helper to read the authenticated username from request/token claims.
src/backend/joanie/core/utils/jwt_tokens.py	Generates Keycloak-shaped tokens when an issuer is configured.
src/backend/joanie/settings.py	Makes SimpleJWT configurable for Keycloak and allows Keycloak token class.
src/backend/joanie/payment/api.py	Uses shared username extraction helper for credit-card ownership operations.
src/backend/joanie/core/filters/client/certificate.py	Uses shared username extraction helper in certificate filtering.
src/backend/joanie/core/api/client/init.py	Replaces repeated auth-username extraction with the shared helper across many endpoints.
src/backend/joanie/tests/base.py	Updates test token generation to support Keycloak token shapes.
src/backend/joanie/tests/core/test_api_base.py	Adds coverage for token generation when Keycloak issuer is configured.
src/backend/joanie/tests/core/test_models_user.py	Adds Keycloak-oriented user sync tests and settings patches.
src/backend/joanie/tests/core/test_models_user.perf.yml	Updates perf expectations for user sync queries (incl. Keycloak case).
src/backend/joanie/tests/core/test_authentication_delegated_jwt_authentication.py	Adds a Keycloak-focused test class for delegated JWT auth behavior.
src/backend/joanie/tests/core/test_api_courses_contract.perf.yml	Updates perf expectations to include user sync UPDATE query.
src/backend/joanie/tests/core/test_api_course_accesses.perf.yml	Updates perf expectations to include user sync UPDATE query.
src/backend/joanie/tests/core/test_api_contract.perf.yml	Updates perf expectations to include user sync UPDATE query.
src/backend/joanie/tests/core/api/organizations/test_list.perf.yml	Updates perf expectations to include user sync UPDATE query.
src/backend/joanie/tests/core/api/organizations/test_api_organizations_contract.perf.yml	Updates perf expectations to include user sync UPDATE query.
src/backend/joanie/tests/core/api/organizations/test_api_organizations_agreements.perf.yml	Updates perf expectations to include user sync UPDATE query.
src/backend/joanie/tests/core/api/organizations/test_api_organization_accesses.perf.yml	Updates perf expectations to include user sync UPDATE query.
src/backend/joanie/tests/core/api/order/test_create.perf.yml	Updates perf expectations to include user sync UPDATE query.
env.d/development/common.dist	Documents env vars for Keycloak integration and JWT claim mapping.

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