Split Login and Register, enable OIDC Registration.

[uwwint]

This change introduces the ability to configure OIDC registration endpoints. In order to achieve this functionality Login and Register need to be split. The new functionality will do the following:

1. Add enduser registration endpoint to oidc_backends.xml

2. Expose them in /api/configuration

3. Add a galaxy configuration option to disable local accounts

4. Change the frontend to:
   a. Split Login / Registration into two buttons
   

   b. In case only one OIDC provider is configured and local accounts are disabled, Login will redirect the user to the OIDC endpoint.
   In case local accounts are enabled the behavior of previous galaxy is retained.
   
   c) In case local accounts are disabled and one OIDC provider with end user registration endpoint exists register will redirect the user straight to the registration of the OIDC provider.
   In case no OIDC provider with end user registration is configured and local accounts are disabled, or local registration is disabled in galaxy.yml, registration is not shown on the UI (as per current behavior)
   If more than one OIDC provider with an endpoint are defined, or local accounts are enabled the Registration page will show all options.

How to test the changes?

(Select all options that apply)

• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  In order to test oidc registration, or disabling local accounts manual testing is still required. The best way is to test the following:
  1. disable local accounts, and configure one OIDC provider -> Only Login is visible on the UI, clicking login will directly point the user to the OIDC login.
  2. Enable local accounts and configure one OIDC provider -> Behavior as today.
  3. Enable local accounts and configure one OIDC provider with end user registration endpoint -> Registration page shows button <Register with ...>

3. Disable local accounts and configure one OIDC provider with end user registration endpoint -> Clicking registration will redirect the user to the end user registration point.

License

• I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.

[uwwint]

@dannon

[ahmedhamidawan]

Thanks for these changes @uwwint !!!
I've made some minor styling/refactoring/linting/import ordering etc fixes, used Galaxy base components ...

Will try out all the use cases you've added next!