Started refactor for merge of OIDC

- Made oidc config more generic to not be overly reliant on the library
  based upon learnings from saml2 auth.
- Removed any settings that are redundant or not deemed required for
  initial implementation.
- Reduced some methods down where not needed.
- Renamed OpenID to OIDC
- Updated .env.example.complete to align with all options and their
  defaults

Related to #2169

app/Config/oidc.php

@@ -0,0 +1,30 @@
+<?php
+
+return [
+
+    // Display name, shown to users, for OpenId option
+    'name' => env('OIDC_NAME', 'SSO'),
+
+    // Dump user details after a login request for debugging purposes
+    'dump_user_details' => env('OIDC_DUMP_USER_DETAILS', false),
+
+    // Attribute, within a OpenId token, to find the user's display name
+    'display_name_claims' => explode('|', env('OIDC_DISPLAY_NAME_CLAIMS', 'name')),
+
+    // OAuth2/OpenId client id, as configured in your Authorization server.
+    'client_id' => env('OIDC_CLIENT_ID', null),
+
+    // OAuth2/OpenId client secret, as configured in your Authorization server.
+    'client_secret' => env('OIDC_CLIENT_SECRET', null),
+
+    // The issuer of the identity token (id_token) this will be compared with what is returned in the token.
+    'issuer' => env('OIDC_ISSUER', null),
+
+    // Public key that's used to verify the JWT token with.
+    // Can be the key value itself or a local 'file://public.key' reference.
+    'jwt_public_key' => env('OIDC_PUBLIC_KEY', null),
+
+    // OAuth2 endpoints.
+    'authorization_endpoint' => env('OIDC_AUTH_ENDPOINT', null),
+    'token_endpoint' => env('OIDC_TOKEN_ENDPOINT', null),
+];