docs: def process_login(context, request):
      """Authenticate username and password and log in user"""
      username = request.json['username']
      password = request.json['password']
  
      # Do the password validation.
      user = context.authenticate(username, password)
      if not user:
          @request.after
          def adjust_status(response):
              response.status = 401
          return {
              'status': 'error',
              'error': {
                  'code': 401,
                  'message': 'Invalid Username / Password'
              }
          }
  
      @request.after
      def remember(response):
          """Remember the identity of the user logged in."""
          # We pass the extra info to the identity object.
          response.headers.add('Access-Control-Expose-Headers', 'Authorization')
          identity = user.identity
          request.app.remember_identity(response, request, identity)
  
      return {
          'status': 'success'
      }