test: add comprehensive tests for session resource templates

- Add sessionTestClientWithResourceTemplates mock
- Test AddSessionResourceTemplate and AddSessionResourceTemplates
- Test DeleteSessionResourceTemplates
- Test session template override behavior
- Test notification behavior (enabled/disabled)
- Test uninitialized session handling
- Test error cases for unsupported sessions
- Verify thread-safety through existing patterns

Coverage increased from 70.17% to 72.8% (+2.63%)

Author: ezynda3