Refactor clustering app

[ujh]

First step towards a more generic version of the clustering app.

[codecov]

Codecov Report

Attention: Patch coverage is 95.00000% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 71.74%. Comparing base (dde8203) to head (77e251a).

Files	Patch %	Lines
...avascript/src/admin/micro-clusters/loadClusters.js	94.44%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2153      +/-   ##
==========================================
+ Coverage   71.58%   71.74%   +0.16%     
==========================================
  Files         234      236       +2     
  Lines        4012     4010       -2     
  Branches      159      156       -3     
==========================================
+ Hits         2872     2877       +5     
+ Misses       1120     1115       -5     
+ Partials       20       18       -2     

Flag	Coverage Δ
javascript	56.86% <95.00%> (+0.43%)	⬆️
ruby	79.91% <ø> (ø)

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