feat: add volume_attachment module (#622)

##### SUMMARY

Added `volume_attachment` as centralized module for attaching and
detaching volumes from servers.

Fixes #490

##### ISSUE TYPE
- New Module Pull Request

##### COMPONENT NAME
`volume_attachment`

---------

Co-authored-by: jo <ljonas@riseup.net>

plugins/modules/volume_attachment.py

@@ -0,0 +1,203 @@
+#!/usr/bin/python
+
+# Copyright: (c) 2025, Hetzner Cloud GmbH <info@hetzner-cloud.de>
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+
+
+from __future__ import annotations
+
+DOCUMENTATION = """
+---
+module: volume_attachment
+
+short_description: Manage the attachment of Hetzner Cloud Volumes
+
+
+description:
+    - Attach and detach Volumes from Hetzner Cloud Servers.
+
+author:
+    - Amirhossein Shaerpour (@shaerpour)
+
+options:
+    volume:
+        description:
+            - Name or ID of the Hetzner Cloud Volume to attach/detach.
+        type: str
+        required: true
+    server:
+        description:
+            - Name or ID of the Hetzner Cloud Server to attach the Volume to.
+            - Required if O(state=present).
+        type: str
+    automount:
+        description:
+            - Automatically mount the Volume in the Server.
+        type: bool
+    state:
+        description:
+            - State of the Volume.
+        type: str
+        default: present
+        choices: [ present, absent ]
+
+extends_documentation_fragment:
+    - hetzner.hcloud.hcloud
+"""
+
+EXAMPLES = """
+- name: Attach my-volume to my-server
+  hetzner.hcloud.volume_attachment:
+    volume: my-volume
+    server: my-server
+
+- name: Detach my-volume from my-server
+  hetzner.hcloud.volume_attachment:
+    volume: my-volume
+    state: absent
+
+- name: Attach my-volume using id to my-server with automount enabled
+  hetzner.hcloud.volume_attachment:
+    volume: 123456
+    server: my-server
+    automount: true
+    state: present
+"""
+
+RETURN = """
+hcloud_volume_attachment:
+    description: The relationship between a Server and a Volume
+    returned: always
+    type: complex
+    contains:
+        volume:
+            description: Name of the Volume
+            type: str
+            returned: always
+            sample: my-volume
+        server:
+            description: Name of the attached Server
+            type: str
+            returned: always
+            sample: my-server
+"""
+
+from ansible.module_utils.basic import AnsibleModule
+
+from ..module_utils.hcloud import AnsibleHCloud
+from ..module_utils.vendor.hcloud import HCloudException
+from ..module_utils.vendor.hcloud.servers import BoundServer
+from ..module_utils.vendor.hcloud.volumes import BoundVolume
+
+
+class AnsibleHCloudVolumeAttachment(AnsibleHCloud):
+    represent = "hcloud_volume_attachment"
+
+    # We must the hcloud_volume_attachment name instead of hcloud_volume, because
+    # AnsibleHCloud.get_result does funny things.
+    hcloud_volume_attachment: BoundVolume | None = None
+    hcloud_server: BoundServer | None = None
+
+    def _prepare_result(self):
+        return {
+            "volume": self.hcloud_volume_attachment.name,
+            "server": (
+                self.hcloud_volume_attachment.server.name if self.hcloud_volume_attachment.server is not None else None
+            ),
+        }
+
+    def _get_volume(self):
+        try:
+            self.hcloud_volume_attachment = self._client_get_by_name_or_id(
+                "volumes",
+                self.module.params.get("volume"),
+            )
+        except HCloudException as exception:
+            self.fail_json_hcloud(exception)
+
+    def _get_server(self):
+        try:
+            self.hcloud_server = self._client_get_by_name_or_id(
+                "servers",
+                self.module.params.get("server"),
+            )
+        except HCloudException as exception:
+            self.fail_json_hcloud(exception)
+
+    def attach_volume(self):
+        self.module.fail_on_missing_params(required_params=["server"])
+
+        try:
+            self._get_volume()
+            self._get_server()
+
+            if self.hcloud_volume_attachment.server is not None:
+                if self.hcloud_volume_attachment.server.id == self.hcloud_server.id:
+                    return
+
+                if not self.module.check_mode:
+                    action = self.hcloud_volume_attachment.detach()
+                    action.wait_until_finished()
+
+                self.hcloud_volume_attachment.server = None
+                self._mark_as_changed()
+
+            if not self.module.check_mode:
+                action = self.hcloud_volume_attachment.attach(
+                    server=self.hcloud_server,
+                    automount=self.module.params.get("automount"),
+                )
+                action.wait_until_finished()
+
+            self.hcloud_volume_attachment.server = self.hcloud_server
+            self._mark_as_changed()
+
+        except HCloudException as exception:
+            self.fail_json_hcloud(exception)
+
+    def detach_volume(self):
+        try:
+            self._get_volume()
+
+            if self.hcloud_volume_attachment.server is not None:
+                if not self.module.check_mode:
+                    action = self.hcloud_volume_attachment.detach()
+                    action.wait_until_finished()
+
+                self.hcloud_volume_attachment.server = None
+                self._mark_as_changed()
+        except HCloudException as exception:
+            self.fail_json_hcloud(exception)
+
+    @classmethod
+    def define_module(cls):
+        return AnsibleModule(
+            argument_spec=dict(
+                volume={"type": "str", "required": True},
+                server={"type": "str"},
+                automount={"type": "bool"},
+                state={
+                    "choices": ["present", "absent"],
+                    "default": "present",
+                },
+                **super().base_module_arguments(),
+            ),
+            supports_check_mode=True,
+        )
+
+
+def main():
+    module = AnsibleHCloudVolumeAttachment.define_module()
+
+    hcloud = AnsibleHCloudVolumeAttachment(module)
+    state = module.params["state"]
+    if state == "present":
+        hcloud.attach_volume()
+    elif state == "absent":
+        hcloud.detach_volume()
+
+    module.exit_json(**hcloud.get_result())
+
+
+if __name__ == "__main__":
+    main()