[S] Working acceptance test (#913)

[SebastianPlace]

The aim of this PR is to get a single basic acceptance test working to lay the foundation for further acceptance tests.

Adding our first acceptance test seemed to somehow change the state of the testing environment causing other tests to complain about missing dependencies e.g. needs: ['service:metrics']. It is for this reason that 20 files have been changed, so don't be too scared to review this.

This PR should be merged before any other acceptance tests can be written.

Changes:

• Added metrics service to test dependencies to fix failing integration tests.
• Created simple acceptance test to assert that a user can always get to help
• Add mirage to stub api endpoints

Closes https://github.com/repositive/discover.repositive.io/issues/913

[pablobm]

Just rebased this on top of master so that we could use it in our work.

[Istar-Eldritch]

I'm closing this PR due do inactivity. Feel free to reopen.