feat(auth): refactor auth, add oidc

Thanks to all HedgeDoc team members for the time discussing,
helping with weird Nest issues, providing feedback
and suggestions!

Co-authored-by: Philip Molares <philip.molares@udo.edu>
Signed-off-by: Philip Molares <philip.molares@udo.edu>
Signed-off-by: Erik Michelson <github@erik.michelson.eu>

frontend/src/components/common/user-avatar/user-avatar-for-user.tsx

@@ -19,5 +19,5 @@ export interface UserAvatarForUserProps extends Omit<UserAvatarProps, 'photoUrl'
  * @param props remaining avatar props
  */
 export const UserAvatarForUser: React.FC<UserAvatarForUserProps> = ({ user, ...props }) => {
-  return <UserAvatar displayName={user.displayName} photoUrl={user.photoUrl} {...props} />
+  return <UserAvatar displayName={user.displayName} photoUrl={user.photoUrl} username={user.username} {...props} />
 }