At the moment a repository reference is needed for webhooks. With the
upcoming package PR we need to send webhooks without a repository
reference. For example a package is uploaded to an organization. In
theory this enables the usage of webhooks for future user actions.
This PR removes the repository id from `HookTask` and changes how the
hooks are processed (see `services/webhook/deliver.go`). In a follow up
PR I want to remove the usage of the `UniqueQueue´ and replace it with a
normal queue because there is no reason to be unique.
Co-authored-by: 6543 <6543@obermui.de>
