…tion

TokenFederationProvider wraps an underlying auth provider (PAT, OAuth, M2M)
and only adds a token-exchange step. The telemetry helpers previously fell
through to AuthMech.OTHER with no flow, hiding the actual auth method.
Unwrap and recurse on external_provider so federated PAT reports PAT,
federated M2M reports CLIENT_CREDENTIALS, etc.

Co-authored-by: Isaac

Build real TokenFederationProvider instances (instead of MagicMocks) so
attribute renames on external_provider break the test rather than passing
silently. Add a payload-serialization assertion confirming the federated
PAT case emits "auth_mech": "PAT" in the JSON event, and a None-inner-
provider edge case.

Co-authored-by: Isaac

Sets the mocked Session's auth_provider to a real TokenFederationProvider
wrapping AccessTokenAuthProvider, then asserts the captured
DriverConnectionParameters reports auth_mech=PAT. This catches regressions
in the wiring at client.py:383-384 (e.g., wrong provider passed to
TelemetryHelper) that the helper-only tests would miss.

Co-authored-by: Isaac