feat(core): Expose context authn methods #6871

Job	Run time
benchmark tests	4m 38s
go (examples)	54s
go (sdk)	1m 49s
image build	1m 39s
go (service)	3m 28s
go (lib/ocrypto)	59s
integration tests	5m 48s
go (lib/fixtures)	1m 0s
go (lib/flattening)	58s
license check	50s
Protocol Buffer Lint and Gencode Up-to-date check	1m 2s
otdfctl e2e tests	4m 48s
platform-xtest / cross-client-test	9m 21s
ci	1s
	37m 15s

Provide feedback