Refactor auth-provider code paths a little. Add Azure support.

[brendandburns]

No description provided.

[codecov-io]

Codecov Report

Merging #74 into master will decrease coverage by 0.37%.
The diff coverage is 72.72%.

@@            Coverage Diff             @@
##           master      #74      +/-   ##
==========================================
- Coverage   93.51%   93.14%   -0.38%     
==========================================
  Files          11       11              
  Lines         972      977       +5     
==========================================
+ Hits          909      910       +1     
- Misses         63       67       +4

Impacted Files	Coverage Δ
config/kube_config_test.py	93.51% <100%> (ø)	⬆️
config/kube_config.py	88.47% <64.7%> (-1.3%)	⬇️

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[brendandburns]

@mbohlool @roycaihw can I get a quick review on this?

Thanks!

[roycaihw]

/lgtm
/approve