Custom OIDC Login

Please search the existing issues for relevant feature requests, and use the reaction feature (https://blog.github.com/2016-03-10-add-reactions-to-pull-requests-issues-and-comments/) to add upvotes to pre-existing requests.

#### Feature Description
- I want to use OIDC login but that requires an enterprise license. Is there a way for me to build my own OIDC Login or check to see if we can extend the current Consul to enable a free OIDC setup?

#### Use Case(s)

- Users who dont have the enterprise license can still use OIDC login for small uses cases.
- Be able to have a community driven implementation of the OIDC process.

Start by searching existing Consul issues for OIDC and related authentication feature requests, as requested in the issue. Then review the current enterprise OIDC login behavior and determine whether a community-supported implementation can be scoped without the enterprise license. Done requires a documented, agreed implementation scope rather than only adding reactions to existing requests.

Written by the indexing model from the issue text.