Proposed changes

Add unreferenced file support to the mock management plane and add integration tests for it.

When sending a config apply request through the mock, the mock looks at the request body to identify unreferenced files. Here is a sample request body of a config apply that contains an unreferenced file:

   {
        "unreferencedFiles": [
            {
                "file_meta": {
                    "name": "/opt/homebrew/etc/nginx/test/unreferenced.conf",
                    "permissions": "0644"
                }
            }
        ]
    }

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING document
• I have run make install-tools and have attached any dependency changes to this pull request
• If applicable, I have added tests that prove my fix is effective or that my feature works
• If applicable, I have checked that any relevant tests pass after adding my changes
• If applicable, I have updated any relevant documentation (README.md)
• If applicable, I have tested my cross-platform changes on Ubuntu 22, Redhat 8, SUSE 15 and FreeBSD 13