tests/auth: Add client and sever interceptor tests

tests/auth/__init__.py

tests/auth/data/jwt-hs256-conflicting.secret

tests/auth/data/jwt-hs256-expired.token

tests/auth/data/jwt-hs256-matching.secret

tests/auth/data/jwt-hs256-unbounded.token

tests/auth/data/jwt-hs256-valid.token

tests/auth/data/jwt-rs256-conflicting.pub.key

tests/auth/data/jwt-rs256-expired.token

tests/auth/data/jwt-rs256-matching.priv.key

tests/auth/data/jwt-rs256-matching.pub.key

tests/auth/data/jwt-rs256-unbounded.token

tests/auth/data/jwt-rs256-valid.token

tests/auth/test_client.py

tests/auth/test_interceptor.py