code: def init_config(self, app):
          
          for k in dir(config):
              if k.startswith('OAUTHCLIENT_'):
                  app.config.setdefault(k, getattr(config, k))
  
          @app.before_first_request
          def override_template_configuration():
              """Override template configuration."""
              template_key = app.config.get(
                  'OAUTHCLIENT_TEMPLATE_KEY',
                  'SECURITY_LOGIN_USER_TEMPLATE'  # default template key
              )
              if template_key is not None:
                  template = app.config[template_key]  # keep the old value
                  app.config['OAUTHCLIENT_LOGIN_USER_TEMPLATE_PARENT'] = template
                  app.config[template_key] = app.config.get(
                      'OAUTHCLIENT_LOGIN_USER_TEMPLATE',
                      'invenio_oauthclient/login_user.html'
                  )
docs: Initialize configuration.