oathkeeper create custom forward request authenticator

Adds a new authenticator which forwards the requests to an upstream service to perform the authentication. This adds the possibility to authenticate a request where the request body is needed.

Related issue(s)

Related to issue #841

Checklist

[x] I have read the contributing guidelines.
[x] I have referenced an issue containing the design document if my change introduces a new feature.
[x] I am following the contributing code guidelines.
[x] I have read the security policy.
[x] I confirm that this pull request does not address a security vulnerability. If this pull request addresses a security. vulnerability, I confirm that I got green light (please contact [email protected]) from the maintainers to push the changes.
[x] I have added tests that prove my fix is effective or that my feature works.
[x] I have added or changed the documentation.

Apr 04 '22 08:04 vladr11

All committers have signed the CLA.

Apr 04 '22 08:04 CLAassistant

Codecov Report

Attention: 38 lines in your changes are missing coverage. Please review.

Comparison is base (6e3844e) 78.05% compared to head (53ead8f) 77.57%. Report is 126 commits behind head on master.

Files	Patch %	Lines
pipeline/authn/authenticator_remote_json.go	60.41%	29 Missing and 9 partials :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #949      +/-   ##
==========================================
- Coverage   78.05%   77.57%   -0.49%     
==========================================
  Files          83       84       +1     
  Lines        3992     4089      +97     
==========================================
+ Hits         3116     3172      +56     
- Misses        597      628      +31     
- Partials      279      289      +10

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