Added authorize controller. Added show action which shows third-party app authentication page. User can allow or deny third-party apps in authentication page.
Added by_signed_jwt method in manifest model which retrieves manifest details from JWT.
Added verify action to the authorize controller. This action is used to check the signed manifest and authorize an app if the manifest is ok.
Added a background worker to post app's callbacks url. Added Authenticator module.
Added send_refresh_token_to_app method to Authenticator lib.