[Feature Request] Add automated build system for images using webhooks from a git repo

[ibnesayeed]

Since a generic webhooks system (#1663, #2161) is now merged and building images from the Git repo is already supported (#1667), we can implement a DockerHub-like automated build system for local images, ready to be deployed. Optionally, these images can be pushed to an associated private registry (#56).

For UI, we can borrow ideas from the DockerHub's automated build configuration page to trigger builds based on pushes to all or certain branches/tags with pattern-based image tag manipulation options.

Additionally, the system should also allow associating services to be deployed when an image is built successfully.