Administration of (non-GitLab) Docker container registry users

Proposal

Allow project & group owners/masters to add custom users to the Docker container registry with read-only access.

Description

Currently, only members of a project can access Docker images that are pushed to the container registry for that particular project.

It would be nice if you can grant access to Docker images of a certain project/group to other non-GitLab users (or even make them public). For example, we want to use Docker images built by GitLab runners in our production & development environment using Rancher (see http://rancher.com/). To add a registry, you must fill in the form below:

It would be a bad practice to fill in the username and password of a GitLab team member here. It would be better to create a custom user that has no access to the source files in GitLab, but only read (pull) access to the registry.

~"feature proposal"