feat: add `delegate` authenticator

Problem Summary

This merge request addresses issue #669 surrounding the behavior of the "noop" authentication method, which underwent changes in commit 6f8ab4f7d. Reverting these changes to restore the previous behavior is challenging due to the potential for breaking existing systems. To mitigate this risk, we propose implementing a new authenticator named "delegate" to replicate the original behavior of the "noop" method.

Ideal Solution

To address this issue, our proposed solution is to implement a new authenticator named "delegate" that replicates the original behavior of the "noop" method. This approach ensures that existing systems in production remain stable and unaffected by changes, while also providing users who prefer the old behavior with an option to utilize it. By introducing the "delegate" authenticator, we mitigate the risk of breaking changes while offering flexibility to users who require the previous behavior.

Changes Proposed

New Authenticator Module: This MR adds a new authenticator module named "delegate" to replicate the original behavior of the "noop" method.
Integration Tests: Integration tests will be added to validate the functionality of the "delegate" authenticator, ensuring compatibility and reliability.
Documentation Updates: Documentation will be updated to include details about the new "delegate" authenticator, its configuration options, and usage examples.

closes 1152

Related issue(s)

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 the approval (please contact security@ory.sh) 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.

ory / oathkeeper