JSON-formatted '/status' API response + generic cleanup

[ipspace]

The /status API call can now return usable JSON data

[ipspace]

@sdargoeuves @captainpacket -- here's the API implementation of "netlab status" as a usable data structure.

I also did a bit of a cleanup, hopefully resulting in a more generic "get" method that can handle multiple multi-part requests.

I wanted to retain the "old" /status results in case anyone already uses them, so you get the JSON data structure back only with "/status/json" or "/status/json/instance". I would love to have a better idea how to handle that. Any suggestions?

[Copilot]

Pull request overview

This PR adds JSON-formatted responses to the /status API endpoint and refactors the API request handler routing logic for better maintainability.

Changes:

• Added generic send_reply and send_error helper functions for consistent response handling
• Enhanced /status endpoint to support JSON output and instance-specific queries
• Refactored GET request routing to use separate handler dictionaries for simple and path-based endpoints
• Updated default bind address to use external_commands.get_local_addr() instead of hardcoded localhost
• Added KeyboardInterrupt handling and improved server startup logging with protocol information

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 7 comments.

[ipspace]

I would love to have a better idea how to handle that. Any suggestions?

Lacking any better ideas, I went for the query string (having "json" in URL seemed awkward) with an environment variable as a fallback mechanism (and "json" as default). This allows an implementations to set an environment variable before starting the API server to keep using the old API format .

FYI @sdargoeuves @captainpacket