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/exp/zone.py

@@ -0,0 +1,40 @@
+"""
+The `exp.zone` module is a namespace that holds experimental features for the `hcloud-python`
+library, breaking changes may occur within minor releases.
+"""
+
+from __future__ import annotations
+
+__all__ = [
+    "is_txt_record_quoted",
+    "format_txt_record",
+]
+
+
+def is_txt_record_quoted(value: str) -> bool:
+    """
+    Check whether a TXT record is already quoted.
+
+    - hello world	=> false
+    - "hello world"	=> true
+    """
+    return value.startswith('"') and value.endswith('"')
+
+
+def format_txt_record(value: str) -> str:
+    """
+    Format a TXT record by splitting it in quoted strings of 255 characters.
+    Existing quotes will be escaped.
+
+    - hello world	=> "hello world"
+    - hello "world"	=> "hello \"world\""
+    """
+    value = value.replace('"', '\\"')
+
+    parts = []
+    for start in range(0, len(value), 255):
+        end = min(start + 255, len(value))
+        parts.append('"' + value[start:end] + '"')
+    value = " ".join(parts)
+
+    return value