Better UX for setting of input schema on hook service parameters

[Marak]

The current method for setting input schemas is clunky. It requires manually appending an additional .schema property to the module.exports scope of the hook service code itself.

This wasn't really by design, but rather out of necessity of the first versions of the software ( when Github Gist was the only option for hook source code ).

Moving forward, we should implement a UI and API endpoints for easily modifying the input schema of a hook and even perhaps showing the auto-form ( current method of setting form theme manually is unintuitive )

Should be relatively easy to implement. Medium priority.

[Marak]

You should now be able to set the schema using a basic textarea form on the /admin page for the service. Works for any language.

This is a great start.

Going to keep this issue open until we can improve the UX from a textarea into something a bit easier to use ( like a visual schema builder ).