Crowd auto update

[nitinsubz]

This PR implements Crowd automatic linking with the CLAM.

Here is how it's structured:

A list of approved domains is maintained in a new tab of the admin tools at endpoint /admin/manage-domains

Every time a user links their ONF account, a function is run to check if their email domain is in the list of approved domains. If it is, they are automatically added to the crowd group through a firebase cloud function.

Every time a user UNlinks their ONF account, a cloud function is run to check if they are in the crowd group. If they are, they are removed from the crowd group.

If a domain is removed from the admin list, then a cloud function is run to remove all crowd users under that domain. The inverse happens when a domain is added to the admin list.

Fixes #275

[codecov[bot]]

Codecov Report

Merging #276 (46ed7af) into master (2a8785b) will increase coverage by 1.59%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #276      +/-   ##
==========================================
+ Coverage   89.77%   91.37%   +1.59%     
==========================================
  Files           9       10       +1     
  Lines         313      371      +58     
  Branches       22       24       +2     
==========================================
+ Hits          281      339      +58     
  Misses         32       32              

Impacted Files	Coverage Δ
common/model/domain.js	100.00% <100.00%> (ø)
common/test_helpers/firestore.mock.js	100.00% <100.00%> (ø)

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