communities: initial release

* Introduces communities module.
* Includes tests for views and Community model.

Signed-off-by: Grzegorz Szpura <grzegorz.szpura@cern.ch>
Co-authored-by: Grzegorz Szpura <grzegorz.szpura@cern.ch>
Merge remote-tracking branch 'gszpura/pu-communities' into pu