Define a role for unregister-member command and delete the referenced secret when unregistering the member

[metlos]

This is a simple PR to also delete the secret together with the ToolchainCluster resource when unregistering the member.

[MatousJobanek]

closing in favor of #99 as it take care of the case when the secret is already removed

[codecov]

Codecov Report

Attention: Patch coverage is 14.28571% with 6 lines in your changes missing coverage. Please review.

Project coverage is 67.71%. Comparing base (ec701fa) to head (21890b8).

Files with missing lines	Patch %	Lines
pkg/cmd/adm/unregister_member.go	14.28%	4 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #98      +/-   ##
==========================================
- Coverage   67.83%   67.71%   -0.12%     
==========================================
  Files          44       44              
  Lines        3264     3271       +7     
==========================================
+ Hits         2214     2215       +1     
- Misses        853      857       +4     
- Partials      197      199       +2     

Files with missing lines	Coverage Δ
pkg/cmd/adm/unregister_member.go	49.01% <14.28%> (-5.53%)	⬇️