CS fixes
Standardize return null;
Add EndpointTrait
Add FQCN
Removed unused use
Merge pull request #6229 from lucasmichot/5.0-endpoint-trait

[5.0] Add EndpointTrait
Merge pull request #6224 from GrahamCampbell/5.0-cs

[5.0] CS Fixes
Merge pull request #6227 from lucasmichot/5.0-return-null

[5.0] Standardize return null;