As discussed in the comments in PR #1197. Also add documenation
accordingly.
One thing I'm not sure about is the simple check in health.go if the
address is usable in the GET request or not. From reading
https://pkg.go.dev/net#Dial it seems that the only non-standard address
format that would work in the `net` package but not in a GET url would
likely only be `:port`, as the others listed here are actually also
valid urls:
`For TCP, UDP and IP networks, if the host is empty or a literal
unspecified IP address, as in ":80", "0.0.0.0:80" or "[::]:80" for TCP
and UDP, "", "0.0.0.0" or "::" for IP, the local system is assumed.`
One additional thing I noticed is that while `WOODPECKER_SERVER_ADDR`
and `WOODPECKER_SERVER_ADDR` use the default value format of `:PORT`,
`WOODPECKER_SERVER` actually uses `localhost:9000`. I guess it makes a
bit of sense, considering the server might not be local to the agent,
but it looks a bit inconsistent this way. I don't think it would hurt to
make the `WOODPECKER_HEALTHCHECK_ADDR` in this format too, but then it's
different from the server flags again... :-)
* Refactor: Move agent stats structs to agent/
Based in part on changes by laszlocph (kube branch):
7f4a0c8c12 Factor into Runner
f7fe9edd0b Using Runner in server
* Refactor: Add Runner constructor with counter field
Based in part on changes by laszlocph (kube branch):
7f4a0c8c12 Factor into Runner
f7fe9edd0b Using Runner in server
* Refactor: Move Runner to agent/ package
Based in part on changes by laszlocph (kube branch):
7f4a0c8c12 Factor into Runner
f7fe9edd0b Using Runner in server
* Refactor: pass pipeline.backend.Engine into agent.Runner
Based in part on changes by laszlocph (kube branch):
7f4a0c8 Factor into Runner
f7fe9ed Using Runner in server
* Use well-known function signature for WriteTo
* Rename stats.go -> state.go
Co-authored-by: Anbraten <anton@ju60.de>
