Sandbox replacement leftovers

[MatousJobanek]

some leftovers of the Sandbox replacements
plus added also a note to the README about the SA namespace locations

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 69.68%. Comparing base (1fbffd4) to head (b91f174).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/cmd/adm/adm.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #76   +/-   ##
=======================================
  Coverage   69.68%   69.68%           
=======================================
  Files          43       43           
  Lines        2570     2570           
=======================================
  Hits         1791     1791           
  Misses        588      588           
  Partials      191      191           

Files with missing lines	Coverage Δ
pkg/cmd/generate/cluster.go	80.00% <ø> (ø)
pkg/cmd/adm/adm.go	0.00% <0.00%> (ø)