Make all module_utils and plugin_utils private (#887)

* Add leading underscore. Remove deprecated module utils.

* Document module and plugin utils as private. Add changelog fragment.

* Convert relative to absolute imports.

* Remove unnecessary imports.

plugins/module_utils/_gnupg/cli.py

@@ -0,0 +1,80 @@
+# Copyright (c) 2023, Felix Fontein <felix@fontein.de>
+# GNU General Public License v3.0+ (see LICENSES/GPL-3.0-or-later.txt or https://www.gnu.org/licenses/gpl-3.0.txt)
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+# Note that this module util is **PRIVATE** to the collection. It can have breaking changes at any time.
+# Do not use this from other collections or standalone plugins/modules!
+
+from __future__ import annotations
+
+import abc
+import os
+
+
+class GPGError(Exception):
+    pass
+
+
+class GPGRunner(metaclass=abc.ABCMeta):
+    @abc.abstractmethod
+    def run_command(
+        self, command: list[str], check_rc: bool = True, data: bytes | None = None
+    ) -> tuple[int, str, str]:
+        """
+        Run ``[gpg] + command`` and return ``(rc, stdout, stderr)``.
+
+        If ``data`` is not ``None``, it will be provided as stdin.
+        The code assumes it is a bytes string.
+
+        Returned stdout and stderr are native Python strings.
+        Pass ``check_rc=False`` to allow return codes != 0.
+
+        Raises a ``GPGError`` in case of errors.
+        """
+        pass
+
+
+def get_fingerprint_from_stdout(stdout: str) -> str:
+    lines = stdout.splitlines(False)
+    for line in lines:
+        if line.startswith("fpr:"):
+            parts = line.split(":")
+            if len(parts) <= 9 or not parts[9]:
+                raise GPGError(
+                    f'Result line "{line}" does not have fingerprint as 10th component'
+                )
+            return parts[9]
+    raise GPGError(f'Cannot extract fingerprint from stdout "{stdout}"')
+
+
+def get_fingerprint_from_file(gpg_runner: GPGRunner, path: str) -> str:
+    if not os.path.exists(path):
+        raise GPGError(f"{path} does not exist")
+    stdout = gpg_runner.run_command(
+        [
+            "--no-keyring",
+            "--with-colons",
+            "--import-options",
+            "show-only",
+            "--import",
+            path,
+        ],
+        check_rc=True,
+    )[1]
+    return get_fingerprint_from_stdout(stdout)
+
+
+def get_fingerprint_from_bytes(gpg_runner: GPGRunner, content: bytes) -> str:
+    stdout = gpg_runner.run_command(
+        [
+            "--no-keyring",
+            "--with-colons",
+            "--import-options",
+            "show-only",
+            "--import",
+            "/dev/stdin",
+        ],
+        data=content,
+        check_rc=True,
+    )[1]
+    return get_fingerprint_from_stdout(stdout)