Setting created_by/updated_by via header

[pacoguzman]

Description

Provide two new configuration settings:

• AuthProxyEnabled to enable retrieving a header to be used on created_by/updated_by
• AuthProxyHeader header to use defaults to X-Email

Motivation and Context

Required at #297

How Has This Been Tested?

Added unit test to ensure this works as expected

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[pacoguzman]

We had this changes in place for sometime now and they work just fine. We set up flagr UI behind an oauth_proxy instance hat forward the X-Email to Flagr

[codecov-io]

Codecov Report

Merging #300 into master will increase coverage by 0.03%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #300      +/-   ##
==========================================
+ Coverage    81.8%   81.83%   +0.03%     
==========================================
  Files          26       26              
  Lines        1533     1536       +3     
==========================================
+ Hits         1254     1257       +3     
  Misses        210      210              
  Partials       69       69

Impacted Files	Coverage Δ
pkg/handler/subject.go	100% <100%> (ø)

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[pacoguzman]

@zhouzhuojie I've applied the feedback ready to review

[pacoguzman]

It seems unit test failed due to other reason https://circleci.com/gh/checkr/flagr/986?utm_campaign=vcs-integration-link&utm_medium=referral&utm_source=github-build-link

[zhouzhuojie]

lgtm, left one comment

[pacoguzman]

Thanks, I've applied the suggetion

[pacoguzman]

Thanks!