feat(channel-vonage): add support for file reception

[laurentlp]

This PR adds support for file reception on channel-vonage

[samuelmasse]

Tested and working 👍

I think this feature needs a better explanation of how it works. I didn't realize the payload.url property was overwritten by the new local url. I also didn't realize I needed to supply {{{event.payload.url}}} as an argument for it to work. I think by default the action should check if payload.url is set and use it without needing to set the type parameter.

Also, I think the type parameter is only doing half of the job. If you decide to pick another property in your payload to pass as a parameter, you still have the new url set to the payload.url property, which isn't ideal. What I would like is to give a path (for example payload.url) and then have the action use _.get(event, path) and _.set(event, path) to get the old url and replace it.

[samuelmasse]

Approved and working for anything under 10mb. We'll need to find a fix for that random 10mb limit in actions