allow null user in kubeconfig's context

[aviramha]

closes #1607

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.

Project coverage is 75.3%. Comparing base (9dd62b9) to head (b3f4c9b).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
kube-client/src/config/file_loader.rs	87.5%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #1608     +/-   ##
=======================================
+ Coverage   75.3%   75.3%   +0.1%     
=======================================
  Files         82      82             
  Lines       7342    7340      -2     
=======================================
+ Hits        5523    5524      +1     
+ Misses      1819    1816      -3     

Files with missing lines	Coverage Δ
kube-client/src/config/file_config.rs	74.2% <ø> (ø)
kube-client/src/config/file_loader.rs	84.0% <87.5%> (+5.2%)	⬆️

[clux]

you are really running into all the degenerate cases 😬

thank you.

[aviramha]

It is a wild wild world out there..
Also, I blame that the upstream is Go so it's not strict thus translation is harder