Log sampling Caddyfile support

[francislavoie]

Our logging stack has sampling support, but it's currently only usable via JSON config. We never wired up Caddyfile config for it.

caddy/logging.go

Line 307 in b285763

Sampling *LogSampling `json:"sampling,omitempty"`

We should add Caddyfile support. This should be easy, it should just be a new option added to the log directive called sampling added in this switch:

caddy/caddyconfig/httpcaddyfile/builtins.go

Line 1000 in b285763

case "format":

And it should take a block of options, i.e. interval, first and thereafter.

[nikonhub]

Hello. I'd like to work on this one :)

[francislavoie]

Go ahead, PRs welcome.