Add TelemetryPolicy test

[silvi-t]

Description

• Adds comprehensive test coverage for TelemetryPolicy custom labels propagation to Limitador metrics
• Implements support for custom user attributes in Keycloak OIDC tokens through new mapper functionality
• Tests verify that user and group labels from both API Key and OIDC authentication correctly appear in Limitador metrics

Changes

New Features

• Keycloak Client Mapper: Added add_user_attribute_mapper() method in testsuite/oidc/keycloak/objects.py:122 to enable custom user attributes in JWT tokens
  • Supports configurable attributes with flexible token claim mapping
  • Controls inclusion in access tokens, ID tokens, and userinfo endpoints

Tests

• TelemetryPolicy Test Suite (testsuite/tests/singlecluster/extensions/telemetry_policy/):
  • test_telemetry_policy_api_key_auth.py: Tests custom labels with API Key authentication
    • Verifies user/group labels from API key annotations appear in Limitador metrics
    • Tests authorized_calls, authorized_hits, and limited_calls metrics
  • test_telemetry_policy_keycloak_auth.py: Tests custom labels with Keycloak/OIDC authentication
    • Verifies user/group labels from OIDC token claims appear in Limitador metrics
    • Tests propagation from Keycloak user attributes
  • conftest.py: Shared fixtures for ServiceMonitor, TelemetryPolicy, and RateLimit policy setup

Testing

• Added parameterized tests covering multiple authentication methods (API Key and OIDC)
• Tests verify label presence and correctness across three metric types
• Includes Prometheus integration to validate metrics scraping and label propagation

Verification Steps

Run the tests using:
poetry run pytest testsuite/tests/singlecluster/extensions/telemetry_policy/test_telemetry_policy_api_key_auth.py
poetry run pytest testsuite/tests/singlecluster/extensions/telemetry_policy/test_telemetry_policy_keycloak_auth.py

Closes #761

[averevki]

Looks nice, tests run for me 👍