This mostly adds connection methods in preparation for the
graphql helper changes.

None of the changes in this commit should cause any observable
effects on application behaviour.

This includes

- removal of pagination tests from resolver specs (resolvers do not -
  currently - know enough of their arguments to make this work). At the
  moment we need to run all our pagination specs at the request
  integration level.

  This is the same for N+1 specs must always be run in request specs,
  since otherwise they are unreliable.