Add access control for portfolio metrics

[mulder999]

Description

The backend now exposes a new configuration setting, acl.portfoliometrics.enabled which allows filtering the main dashboard metrics only to projects granted by ACL.

Addressed Issue

This enhancement allows to adress the backend issue 2323.

By default it is disabled, preserving the original broken behavior to ensure that very large databases with users having huge number of projects granted through ACL are not slow down in any way.

Reference screenshot

Checklist

• [x] I have read and understand the contributing guidelines
• [ ] This PR introduces new or alters existing behavior, and I have updated the documentation accordingly