Implement limactl network (list|create|delete)

[AkihiroSuda]

Fix #3672

e.g.,

$ limactl network create foo --gateway 192.168.42.1/24

$ limactl network list
NAME       MODE       GATEWAY             INTERFACE
bridged    bridged    -                   en0
foo        user-v2    192.168.42.1/24     -
host       host       192.168.106.1/24    -
shared     shared     192.168.105.1/24    -
user-v2    user-v2    192.168.104.1/24    -

$ limactl network list --json foo bridged
{"mode":"user-v2","gateway":"192.168.42.1","netmask":"255.255.255.0"}
{"mode":"bridged","interface":"en0"}

$ limactl network delete foo

[nirs]

$ limactl network list --json foo bridged
{"mode":"user-v2","gateway":"192.168.42.1","netmask":"255.255.255.0"}
{"mode":"bridged","interface":"en0"}

This is not json format, this is jsonlines format:
https://jsonlines.org

Trying to parse this string:

{"mode":"user-v2","gateway":"192.168.42.1","netmask":"255.255.255.0"}
{"mode":"bridged","interface":"en0"}

will not work with most json parsers.

The fact that Go json encoded and decoder supports this format does not make it json.

To make this valid json we need to return a list:

[
  {"mode":"user-v2","gateway":"192.168.42.1","netmask":"255.255.255.0"},
  {"mode":"bridged","interface":"en0"}
]

jsonlines format makes sense for logs when you want to stream the data.

$ limactl network delete foo

How the case of deleting a network in use is handled? For example deleting the shared network when instances are running using it. I think rejecting the request is the simplest way to avoid issues.

If we have command to create/list/delete networks, maybe support also start/stop and simplify socket_vmnet network management?

[AkihiroSuda]

jsonlines

Intentionally adopted for consistency with limactl ls and limactl disk ls

in use

Not handled yet

[nirs]

jsonlines

Intentionally adopted for consistency with limactl ls and limactl disk ls

Makes sense.

Using --json is ok if we document in the help message that we return jsonlines format.
This is easy to handle by reading lines and parsing them separately.

[jandubois]

jsonlines format makes sense for logs when you want to stream the data.

It also makes sense for anything that is processed with a pipeline. It makes your jq commands simpler because you don't need to start with .[]. And you can always wrap the objects in an array with jq -s, but I find I virtually never need that.

FWIW, docker images --format json also uses jsonlines format...