chore: replace domain from .mgmt to .mgmt.local

[gruyaume]

Description

Here, we replace .mgmt with .mgmt.local. This change is required because of a recent change in the webconsole where we do input validation on the upf hostname and .mgmt is not a valid domain.

This PR partly addresses the issue identified here:

• Improve logging with NMS API Calls sdcore-nms-k8s-operator#441

Checklist:

• Documentation follows the Canonical Documentation Style Guide
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that validate the behaviour of the software
• I validated that new and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have bumped the version of the library