Bugfix/set sitecollectionadmins groupified sites

[mloitzl]

set all sharePointAdminLoginNames for groupified sites
improve tests

Fixes #1307

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (63545f3) 82.42% compared to head (41024c1) 81.56%.
Report is 1647 commits behind head on dev.

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Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #1323      +/-   ##
==========================================
- Coverage   82.42%   81.56%   -0.86%     
==========================================
  Files         416      624     +208     
  Lines       28590    43467   +14877     
  Branches        0     4565    +4565     
==========================================
+ Hits        23565    35455   +11890     
- Misses       5025     6663    +1638     
- Partials        0     1349    +1349     

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[jansenbe]

@mloitzl : travelling at the moment, will process this one as soon as possible. Thanks for sharing!