- repo name ruler
  <owner>/<repo_name>[/<image_name>] (note: if `<image_name>` not set,
  will use `<repo_name>` as default)
- add a new repo permission unit named as `package`, it's not a
  real unit in gitea, just use for permission check.
- add a small api `GET /repos/{owner}/{repo}/packages/{type}/{name}` for
  test, maybe can add more later

ref:
- https://docs.docker.com/registry/spec/auth/token/
- https://docs.docker.com/registry/notifications/
- https://github.com/cesanta/docker_auth

Signed-off-by: a1012112796 <1012112796@qq.com>

Co-authored-by: techknowlogick <matti@mdranta.net>

because if using token serve, it will be difficut
to use docker registry api directly, try do
someting to simplify it.`

Signed-off-by: a1012112796 <1012112796@qq.com>

Thanks @wULLSnpAXbWZGYDYyhWTKKspEQoaYxXyhoisqHf