Add support for additional OAuth2 providers

[drey-bigney]

Describe the feature request or enhancement you'd like

As a user of the OSMT open-source project I want to support other OAuth2 providers beyond just OKTA.

OSMT was developed using OKTA as the OAuth2 provider, however we realize that there are a variety of providers in use and the choice of provider will ideally vary based on the user. What effort is required to leverage other providers? (Auth0, Ping, etc?)

Is your feature request related to a problem? Please describe it.

Additional context

This should be a modular solution which allows for future extension to other OAuth2 providers. Will require front end module/component/service and likely modification of the backend SecurityConfig class for Spring security.

[JohnKallies]

This is a clear change around Spring Security and OAuth2/OIDC providers in the Spring app / configs. This may also require alternate implementations in the UI as well. These should be modularized, not peppering UI code with conditionals.