refactor: add service package and start splitting HTTP handling

[ThinkChaos]

Progress for #1206.

No user visible changes in this PR: it's just refactoring and the new config cannot be set from the YAML file.
Instead the new config structs are filled with the info from ports: until we're ready to deprecate ports fully.

The first part of the commits refactor how we setup the HTTP listeners.
The second part adds a new service package with interfaces used to split up server.Server.
The commits after adding that package refactor the DoH, metrics, and API to be services.

Here's the docs that package as an overview of the design:

Package service exposes types to abstract services from the networking.

The idea is that we build a set of services and a set of network
endpoints (Listener). The services are then assigned to endpoints based
on the address(es) they were configured for.

Actual service to endpoint binding is not handled by the abstractions in
this package as it is protocol specific.
The general pattern is to make a "server" that wraps a service, and can
then be started on an endpoint using a Serve method,
similar to http.Server.

To support exposing multiple compatible services on a single endpoint
(example: DoH + metrics on a single port), services can implement Merger.

This doesn't touch DNS listener/server code (besides moving the TLS config to a single spot), but I think we'll be able to re-use the same code to setup DNS listeners, and split the DNS server logic into a bunch of services + one server.

The follow-up work is to continue removing things from configureHTTPRouter until it's empty and we can remove the transitional httpMiscService.
At that point we'll be ready to deprecate ports and switch to the new services config format under discussion in #1206.

[ThinkChaos]

I still need to write tests for the new package, and the various new "services", but besides that it's in a reviewable state :)

[0xERR0R]

Skimmed over your PR and it looks very good! 👍

[kwitsch]

Read through it and I think you did an amazing job. 👍

This approach looks like a really good foundation for a step wise implementation without end-user obstruction.

[codecov]

Codecov Report

Attention: Patch coverage is 90.15385% with 32 lines in your changes missing coverage. Please review.

Please upload report for BASE (refactor/services-dependencies@380906d). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
server/server.go	80.00%	8 Missing and 4 partials ⚠️
config/config.go	0.00%	8 Missing ⚠️
server/doh.go	91.22%	3 Missing and 2 partials ⚠️
metrics/metrics.go	0.00%	4 Missing ⚠️
cmd/serve.go	0.00%	1 Missing and 1 partial ⚠️
metrics/metrics_event_publisher.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@                        Coverage Diff                        @@
##             refactor/services-dependencies    #1427   +/-   ##
=================================================================
  Coverage                                  ?   91.24%           
=================================================================
  Files                                     ?       91           
  Lines                                     ?     5424           
  Branches                                  ?        0           
=================================================================
  Hits                                      ?     4949           
  Misses                                    ?      390           
  Partials                                  ?       85           

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[ThinkChaos]

I'm satisfied with where tests are at now. Codecov doesn't seem to understand the PR being based on a branch that's not targeting main (or maybe it's because I changed it), so there's no explicit percentage diff, but most new code is covered.
The total coverage dropped 2% because I added a suite to the metrics package, but that's just more realistic 😄

Also the e2e tests have been pretty flaky for me today, not sure if it's my changes or not.
Here's an example failure: https://github.com/0xERR0R/blocky/actions/runs/10639898980/job/29498704949

[t-e-s-tweb]

@ThinkChaos I want to test this on my setup but it isn't working. I read through the comments so to make it work in testing I need to change the yaml in config.go?

[ThinkChaos]

@t-e-s-tweb thanks for the interesting and trying it out, this PR doesn't change what's possible to configure yet, just changes the code to make that easy as a follow-up.
What specifically are you trying to do? Maybe I can do that follow-up work to enable your use case

[t-e-s-tweb]

@t-e-s-tweb thanks for the interesting and trying it out, this PR doesn't change what's possible to configure yet, just changes the code to make that easy as a follow-up. What specifically are you trying to do? Maybe I can do that follow-up work to enable your use case

I am using blocky as blocking server over dns-over-https. I want to migrate all dns-over-https handling over to all the new changes in this PR.

[ThinkChaos]

Then building the branch and making no changes to the config should work.
The CopyPortsToServices function in config.go takes care of mapping the existing YAML structure to the new code.

[ThinkChaos]

GitHub auto closed this with no option for me to reopen because the target branch was merged into main.
So I made a new PR: #1595.

(I was hoping GitHub had the same logic as GitLab where merging a MR changes the other MRs targeting that branch to now target where the first MR was merged, but no I guess not)