Add deletion and raw http endpoint urls for Webhooks

[sfinktah]

WHY are these changes introduced?

I couldn't add a webhook, because it insists on making all HttpDelivery webhooks a path of Context::$HOST_NAME (which was myshop.myshopify.com), and I wanted a webhook on my server.

    public function getCallbackAddress(string $path): string
    {
        return 'https://' . Context::$HOST_NAME . '/' . ltrim($path, '/');
    }

I also couldn't delete a webhook.

WHAT is this pull request doing?

Added a new enum to Webhooks::Registry::register

            case self::DELIVERY_METHOD_RAW:
                $method = new HttpDeliveryRaw();
                break;

which doesn't try and get smart with the provided url

    public function getCallbackAddress(string $path): string
    {
        return $path;
    }

To allow deletion of webhooks with the maximum code re-use, I modified Webhooks::Registry::register to equate an empty $path with a request to delete the webhook.

        if (empty($path) && $webhookId) {
            $body = self::sendDeleteRequest(
                $client,
                $topic,
                $callbackAddress,
                $method,
                $webhookId
            );
            $registered = $method->isSuccess($body, $webhookId);
            return new RegisterResponse($registered, $body);
        }

Type of change

• Patch: Bug (non-breaking change which fixes an issue)
• Minor: New feature (non-breaking change which adds functionality)
• Major: Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• I have added a changelog entry, prefixed by the type of change noted above
• [-] I have added/updated tests for this change

• There are no existing tests for DELIVERY_METHOD_HTTP, so no reason to add any for DELIVERY_METHOD_RAW
• Possibly there should be a test written for the deletion functionality, and I will do so if this PR receives tentative approval.

• I have updated the documentation for public APIs from the library (if applicable)
  There's documentation?

[tectiv3]

because it insists on making all HttpDelivery webhooks a path of Context::$HOST_NAME

I also have this problem. Why does it do that?!
Maybe an easier (with a smaller footprint) fix would be to try to detect http in the path?

[sfinktah]

because it insists on making all HttpDelivery webhooks a path of Context::$HOST_NAME

I also have this problem. Why does it do that?! Maybe an easier (with a smaller footprint) fix would be to try to detect http in the path?

Because it's retarded.

Making a clever fix like you suggest is how I would normally solve the problem myself, however with production code it is best not to change the behavior of existing functions.

[sfinktah]

I have signed the CLA!