OR-737 Add the core for searching users not in specific community

* Augment `getUsersList` and `getUsersSearch`
* Add storage tests
* Add a helper for adding users in communities
OR-737 Add the documentation
OR-737 Add a route to search users who can be invited in community

* Add the route `GET /api/communities/:id/invitablepeople`.
* Add the webserver controller
* Add midway tests
OR-737 Fix unit test
OR-737 Update domain controller
fixup! OR-737 Add a route to search users who can be invited in community
fixup! OR-737 Add the core for searching users not in specific community
Merge pull request #525 in OR/rse from ~RPIGNOLET/rse:OR-737 to master

* commit '06483cfcae249dfa5b874def37399f0fc7bcf6ff':
  fixup! OR-737 Add the core for searching users not in specific community
  fixup! OR-737 Add a route to search users who can be invited in community
  OR-737 Update domain controller
  OR-737 Fix unit test
  OR-737 Add a route to search users who can be invited in community
  OR-737 Add the documentation
  OR-737 Add the core for searching users not in specific community
Revert "fixup! OR-737 Add the core for searching users not in specific community"

This reverts commit 06483cfcae249dfa5b874def37399f0fc7bcf6ff.
Revert "fixup! OR-737 Add a route to search users who can be invited in community"

This reverts commit 38624594ce810fccd152b7d43db695a722a9fac5.
Revert "OR-737 Update domain controller"

This reverts commit 22e8f8a2417e567915949f277ac84b90065e215e.
Revert "OR-737 Fix unit test"

This reverts commit 8a56154e7759bf927d7eb66f96c50cf504ca4a95.
Revert "OR-737 Add a route to search users who can be invited in community"

This reverts commit 0f0567daa5de8cf3a1486db2334c51a2758afdbe.
Revert "OR-737 Add the documentation"

This reverts commit 10f6e8cf32e9ccddca3b4b29e7b25edb7a2bfce9.
Revert "OR-737 Add the core for searching users not in specific community"

This reverts commit a3091e0fc7a6a47f26340780d689368e97559f21.