Allow external endpoint on smart action

[whollacsek]

https://github.com/ForestAdmin/forest-express/blob/feb5ecc7658adc68f48e7f3f6dc098d6404c682b/src/services/path.js#L12

It would be great if we can use an external endpoint for smart actions. It is especially useful in a serverless architecture. Currently we need to write an indirection in the routes folder to forward the request.

[louisteenbrink]

@whollacsek have you tried adding the endpoint option to your smart action configuration?