Add (optional) debug logging for console requests

[ramondeklein]

There are cases where issues arise with the console for HTTP request and/or websockets that are hard to debug, because we can't trace the requests. This PR adds functionality to add debug logging middleware that logs HTTP requests (including websockets). This can be enabled by setting the CONSOLE_DEBUG_LOGLEVEL environment variable to one of the following values:

• 0 (default) uses no logging.
• 1 log single line per request for server-side errors (status-code 5xx).
• 2 log single line per request for client-side and server-side errors (status-code 4xx/5xx).
• 3 log single line per request for all requests (status-code 4xx/5xx).
• 4 log details per request for server-side errors (status-code 5xx).
• 5 log details per request for client-side and server-side errors (status-code 4xx/5xx).
• 6 log details per request for all requests (status-code 4xx/5xx).

A single line logging has the following information:

• Remote endpoint (IP + port) of the request. Note that reverse proxies may hide the actual remote endpoint of the client's browser.
• HTTP method and URL
• Status code of the response (websocket connections are hijacked, so no response is shown)
• Duration of the request

The detailed logging also includes all request and response headers (if any).