* Intention to support instantiation of server for
integration testing. Side effect is improving readability.
* Extracts root handler into func.
* Error logging handled by main.

* Intention is to test against package interface
using server_test package. Couldn't get to work
with main_test.
* Side effect is improved readability due to less
global state.
* ghActionsExporter private to package as created
in Server setup

* Intention was to improve coverage of http server
implementation.
* Probably makes more sense to test the handlers
directly for most cases.

* Backfills tests before behaviour changes.
* CheckRun test only checks for 200 due to
async behaviour.

Assumes job queue time can be calculated from difference
between job start time and start time of first step.

Labels:
* runner_group to identify queues for specific runners
* state queued as durations can also be published for
  completed jobs
* no workflow label as it is not possible to identify
  workflow without additional API calls

* Simplifies testing by moving observation of workflow job
metrics under interface.
* Leaves other metrics untouched for now, even though
inconsistent.

* Use custom serve mux to allow for creation of
multiple servers in integration tests.

This is possible as it seems step started_at times are
rounded to the closest second whereas job started_at time
has miliseconds included.