Custom failure app for devise-jwt to respond in JSON format

api_failure_app.rb

# frozen_string_literal: true

module Devise
  # Failure application that will be called every time :warden is thrown from
  # any strategy or hook. This application overrides the default Devise
  # failure application in order to render messages as JSON.
  class ApiFailureApp < Devise::FailureApp
    def respond
      json_api_error_response
    end

    def json_api_error_response
      self.status        = 401
      self.content_type  = 'application/json'
      self.response_body = { errors: [{ message: i18n_message }] }.to_json
    end
  end
end