Build out endpoint to accept image POST requests directly from cell-cam providers

[nathanielrindlaub]

RidgeTec has offered to send JSON payloads w/ any information we need directly to an endpoint if we provide one. That would be a much more resilient approach for ingesting cell-cam images, so I think we should do that, and perhaps reach out to Reconyx to see if they might be amenable to doing the same.

Related: #2 and tnc-ca-geo/animl-api#75.

[nathanielrindlaub]

Update: Reconyx does offer image-forwarding to client endpoints as part of their Enterprise Agreement, endpoint specs here, so we can likely build an endpoint to those specifications and have Ridgetec post similar payloads.

@ingalls is going to set this service up as a separate project.