Fix metric aggregates as non-admin

[Callum027]

When using the aggregates API with a metric ID, the RBAC policy project_id:%(resource.project_id)s" fails to authenticate a non-admin user that is part of the project the metric is also part of via its resource relationship.

This patch fixes two issues preventing this from working:

• Set details=True when listing specified metrics to ensure the joined load with the Metric and Resource models is done.
• Add support for processing oslo.db SQLAlchemy models in gnocchi.rest.api.flatten_dict_to_keypairs to make sure nested attributes are added to the list of targets passed to the policy enforcer.

[Callum027]

Seems like the GitHub Actions runners are having issues.

       Exception in thread Thread-2 (thread_compiler):
      Traceback (most recent call last):
        File "/usr/lib/python3.12/threading.py", line 1073, in _bootstrap_inner
          self.run()
        File "/usr/lib/python3.12/threading.py", line 1010, in run
          self._target(*self._args, **self._kwargs)
        File "/tmp/pip-install-nqpvtzih/uwsgi_8ef73bf3d5474636b57bf345332b6745/uwsgiconfig.py", line 116, in thread_compiler
          ret = subprocess.call(cmdline, shell=True)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/usr/lib/python3.12/subprocess.py", line 389, in call
          with Popen(*popenargs, **kwargs) as p:
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/usr/lib/python3.12/subprocess.py", line 1026, in __init__
          self._execute_child(args, executable, preexec_fn, close_fds,
        File "/usr/lib/python3.12/subprocess.py", line 1955, in _execute_child
          raise child_exception_type(errno_num, err_msg, err_filename)
      OSError: [Errno 14] Bad address: '/bin/sh'