Enable filtering resources by author team membership

This new condition allows resources to be filtered depending on whether an author is a member of the group or project specified.

This will be useful to determine whether a Merge Request or Issue was raised by a Community member or a Team member.

Notes:

The approach for gathering team members is executed per resource and could definitely by made more performant

Closes https://gitlab.com/gitlab-org/gitlab-triage/issues/3 https://gitlab.com/gitlab-org/gitlab-triage/issues/49