This PR was merged into the 7.3 branch. Discussion ---------- [Routing] Validate "namespace" (when using `Psr4DirectoryLoader`) | Q | A | ------------- | --- | Branch? | 7.3 | Bug fix? | no | New feature? | yes  | Deprecations? | no  | Issues | Fix #...  | License | MIT  I spend a small amount of time to understand why my controller was inaccessible: <img width="496" alt="image" src="https://github.com/user-attachments/assets/959188fc-75d3-43db-a4e8-78fc4d140a74" /> With the following configuration: ```yaml controllers: resource: path: ../src/Application/Controller/ namespace: App\Application/Controller type: attribute ``` You may have seen that the namespace `App\Application/Controller` is invalid because the presence of `/` instead of `\`. If I correct it, then my controller is accessible. It means that invalid namespaces are simply ignored without any hints for the user, and I think it can be improved and be more user-friendly :) This PR add namespace validation, it checks if `/` is found, and if namespace is composed of valid PHP identifiers: <img width="759" alt="image" src="https://github.com/user-attachments/assets/ae8d1dc8-f250-4faf-bc07-22aaefc363fd" /> <img width="1011" alt="image" src="https://github.com/user-attachments/assets/7fe97b1e-77be-45ab-b875-b2a67b7501dd" /> Commits ------- 3d807c1 [Routing] Validate "namespace" (when using `Psr4DirectoryLoader`)

Uh oh!