Add API for Webhooks

[fabi125]

Environment

• Python version: 3.6.5
• NetBox version: 2.10.3

Proposed Functionality

Expose the functionality that is currently available in the Admin UI under Extras -> Webhooks via the Rest API to be able to add/update/delete webhooks.

Use Case

We would like to store the webhook configuration in source control and configure Netbox via the API.

See also #5608.

Database Changes

None.

External Dependencies

None.

[cpmills1975]

If web hooks and custom fields are to be exposed via the API, should permissions be as well?

For what it is worth, if you went down the path of using the netbox-docker container, these could be delivered in code via a 'startup-script' injected in to the container when it is brought up - I am currently in the process of using an enormous collection of custom startup-scripts to migrate two NetBox instances in to one and these are all stored in my SCM.

[jeremystretch]

If web hooks and custom fields are to be exposed via the API, should permissions be as well?

There's already a REST API endpoint for permissions.