Improve container credentials retrieval matching container repository names

[pditommaso]

Wave retrieves the container credentials to be used, querying Tower credentials for container-reg provider and looking for a matching registry name for the given repository e.g. docker.io given the repository docker.io/library/ubuntu.

However, this approach limits the possibility of authenticating repositories in the same registry owned by different users or organisations, requiring different credentials.

This issue aims to extend the credentials retrieval mechanism so that the entire container repository name is used to discover the matching credentials to be used, not just the registry name.

The implementation of this feature also requires that Tower allows, optionally, storing the full container name,