Create a GraphQL query for the depedency proxy

We should add a new type for the dependency proxy and a new query to be able to consume the data present in the database through the GraphQL layer.

We would need to have exposed:

• Group settings (enabled/disabled)
• Url
• Stored blobs with digest

Types

• DependencyProxy::Manifest
• DependencyProxy::Blob
• Group::DependencyProxySettings

We can expose the Url (image prefix) within the Group type.