Allow logging in with the default OAuth 2 principal

The default principal is "dev@localhost", if you run the system with the development profile (DEV) a user with sys-admin role will be created with that principal as username.

README.md

@@ -2,6 +2,11 @@
 The web GUI is protected by OAuth 2 log in. Run the Docker Compose containers with
 `docker compose up` to start the authorization server to be able to log in.
 
+If you run SciPro in development mode (DEV profile) you will be able to log in
+as the "default" OAuth 2 user populated in the upper form. If you have other
+data in your database you will have to use the lower form and specify a valid
+username in the principal field.
+
 ## Working with the API
 The API is protected by OAuth 2 acting as a [resource server](https://www.oauth.com/oauth2-servers/the-resource-server/)
 verifying tokens using [token introspection](https://datatracker.ietf.org/doc/html/rfc7662).

core/src/main/java/se/su/dsv/scipro/DataInitializer.java

@@ -200,6 +200,10 @@ public class DataInitializer implements Lifecycle {
         admin.addRole(Roles.SYSADMIN);
         createBeta(admin);
         passwordService.updatePassword(admin, "aey7ru8aefei0jaW2wo9eX8EiShi0aan");
+        Username defaultOAuth2Principal = new Username();
+        defaultOAuth2Principal.setUsername("dev@localhost");
+        defaultOAuth2Principal.setUser(admin);
+        save(defaultOAuth2Principal);
     }
 
     private void createBeta(User user) {