Adding ability to handle webhooks from Github

[randalldfloyd]

Overview

We would like to use forklift for automating deployments of things that are not running in containers. Since a webhook would never be called from DockerHub in those cases, we could call from Github webhooks instead.

This adds an additional endpoint that can parse the format of a GH event payload. It currently only handles the push event, but the event type is being detected so it could be expanded on to handle the many various events GH can send.

Any repo that wants to send an event payload back to forklift from GH would have to use the new endpoint like:

https://location_of_forklift.domain.com/gh_webhook?apikey=xxxxxxxxxxxxx

Configuration

The configuration of the valid_containers section requires knowing how to map the data in the GH event payload to the name and tag values. For the following payload:

{
  "ref": "refs/heads/main",
...
  "repository": {
    "id": 176407102,
...
    "name": "some_repo",
    "full_name": "IUBLibTech/some_repo"
  }  
}

The values in the forklift configuration would be:

valid_containers = {'IUBLibTech/some_repo':
                     [{'tag': 'refs/heads/main', 
                       'target': 'some_deployment_location/bin/update'}]
                   }

[dlpierce]

Yay, GH webhooks!