Development server - handle also the manifests.js file request

[lslezak]

Problem

When running a local development server the list of display languages was empty:

The problem was that the manifests.js file request was not handled by the proxy and the browser received error 404. The manifests contain the list of supported languages.

Solution

Proxy the request to the real Cockpit server, but patch the response with the latest Agama manifest from the current sources. That ensures the supported languages are read from the current source code and not from the remote server (which might support less languages).

Testing

• Tested manually
• To test that injecting the current manifest.json file works I have added the Czech language to the local file (it is actually not supported)