feat: add unix sockets support for URLs

[nlachfr]

Porposal for adding unix sockets support for URLs

Related issue(s)

#871

Checklist

• I have read the contributing guidelines.
• I have referenced an issue containing the design document if my change
  introduces a new feature.
• I am following the
  contributing code guidelines.
• I have read the security policy.
• 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
  security@ory.sh) from the maintainers to push
  the changes.
• I have added tests that prove my fix is effective or that my feature
  works.
• I have added or changed the documentation.

Further Comments

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #874 (a557489) into master (737320f) will increase coverage by 0.11%.
Report is 346 commits behind head on master.
The diff coverage is 72.16%.

@@            Coverage Diff             @@
##           master     #874      +/-   ##
==========================================
+ Coverage   62.47%   62.59%   +0.11%     
==========================================
  Files         102      103       +1     
  Lines        4813     4895      +82     
==========================================
+ Hits         3007     3064      +57     
- Misses       1531     1548      +17     
- Partials      275      283       +8     

Files Changed	Coverage Δ
proxy/proxy.go	67.00% <44.44%> (-3.22%)	⬇️
pipeline/authn/authenticator_cookie_session.go	72.44% <57.69%> (-7.56%)	⬇️
helper/transport.go	78.84% <78.84%> (ø)
pipeline/authn/authenticator_bearer_token.go	69.23% <100.00%> (+4.01%)	⬆️
pipeline/authz/remote.go	80.00% <100.00%> (ø)
pipeline/authz/remote_json.go	96.29% <100.00%> (ø)
rule/validator.go	83.92% <100.00%> (+3.57%)	⬆️

[aeneasr]

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[nlachfr]

I updated my commits signature and agreed to the CLA

[aeneasr]

Thank you! Could you please include tests and documentation to show case how this feature is configured?

[nlachfr]

Regarding documentation, do you think I should add a specific section for unix sockets URIs ?
For now, I have added a small description on fields able to handle it.