Feature/discover endpoint OIDC

[Repumba]

Your checklist for this pull request

• [X] I've read the contributing guideline.
• [X] I've tested my changes by building and running the project, and testing changed functionality (if applicable)
• [ ] I've added automated tests for my change (if applicable, optional)
• [ ] I've updated documentation to reflect my change (if applicable)

What is the current behaviour?

You have to manually fill every field while adding new OAuth provider

What is the new behaviour?

You can input only discovery endpoint and get information about other endpoints automatically.

Test plan

Manual tests

Closing issues

[Repumba]

If you want to test it with keycloak from docker-compose-oidc-dev.yml, use http://keycloak:8080/realms/mwdb-oidc-dev/.well-known/openid-configuration as discovery endpoint

[psrok1]

I thought about reviving this PR but there are significant issues:

• It provides an ability to send arbitrary GET request from the server. In addition, any JSON-like response will be sent back to user as "pure". We also don't check if user is an administrator. This is pretty serious security issue.
• Changes in authentication methods (None, None) that are out of scope for this PR