refactor: mark module_utils modules as private (#782)

##### SUMMARY

All `module_utils` are now marked as **private**. None of the modules
were intended for public use.

Similar to
https://togithub.com/ansible-collections/community.general/issues/11312

plugins/module_utils/_vendor/hcloud/metrics/domain.py

@@ -0,0 +1,51 @@
+from __future__ import annotations
+
+from datetime import datetime
+from typing import Literal
+
+from ..core import BaseDomain
+
+__all__ = [
+    "TimeSeries",
+    "Metrics",
+]
+
+
+TimeSeries = dict[str, dict[Literal["values"], list[tuple[float, str]]]]
+
+
+class Metrics(BaseDomain):
+    """Metrics Domain
+
+    :param start: Start of period of metrics reported.
+    :param end: End of period of metrics reported.
+    :param step: Resolution of results in seconds.
+    :param time_series: Dict with time series data, using the name of the time series as
+        key. The metrics timestamps and values are stored in a list of tuples
+        ``[(timestamp, value), ...]``.
+    """
+
+    start: datetime
+    end: datetime
+    step: float
+    time_series: TimeSeries
+
+    __api_properties__ = (
+        "start",
+        "end",
+        "step",
+        "time_series",
+    )
+    __slots__ = __api_properties__
+
+    def __init__(
+        self,
+        start: str,
+        end: str,
+        step: float,
+        time_series: TimeSeries,
+    ):
+        self.start = self._parse_datetime(start)
+        self.end = self._parse_datetime(end)
+        self.step = step
+        self.time_series = time_series