Add support for container initialization

This commit contributes support for container initialization (i.e., the
operation performed by `podman container init`.)

Alongside that, it introduces:
- unit test ContainersTestCase::test_init
- integration subtest `Create-Init-Start Container` in
  ContainersIntegrationTest::test_container_crud

A small fix to the docstring of Container.status has also been
contributed to reflect the existance of the `created` and `initialized`
states.

Signed-off-by: Riccardo Paolo Bestetti <pbl@bestov.io>

podman/domain/containers.py

@@ -54,7 +54,7 @@ def labels(self):
 
     @property
     def status(self):
-        """Literal["running", "stopped", "exited", "unknown"]: Returns status of container."""
+        """Literal["created", "initialized", "running", "stopped", "exited", "unknown"]: Returns status of container."""
         with suppress(KeyError):
             return self.attrs["State"]["Status"]
         return "unknown"
@@ -262,6 +262,11 @@ def get_archive(
         stat = api.decode_header(stat)
         return response.iter_content(chunk_size=chunk_size), stat
 
+    def init(self) -> None:
+        """Initialize the container."""
+        response = self.client.post(f"/containers/{self.id}/init")
+        response.raise_for_status()
+
     def inspect(self) -> Dict:
         """Inspect a container.
 

podman/tests/integration/test_containers.py

@@ -143,6 +143,24 @@ def test_container_crud(self):
             top_ctnr.reload()
             self.assertIn(top_ctnr.status, ("exited", "stopped"))
 
+        with self.subTest("Create-Init-Start Container"):
+            top_ctnr = self.client.containers.create(
+                self.alpine_image, ["/usr/bin/top"], name="TestInitPs", detach=True
+            )
+            self.assertEqual(top_ctnr.status, "created")
+
+            top_ctnr.init()
+            top_ctnr.reload()
+            self.assertEqual(top_ctnr.status, "initialized")
+
+            top_ctnr.start()
+            top_ctnr.reload()
+            self.assertEqual(top_ctnr.status, "running")
+
+            top_ctnr.stop()
+            top_ctnr.reload()
+            self.assertIn(top_ctnr.status, ("exited", "stopped"))
+
         with self.subTest("Prune Containers"):
             report = self.client.containers.prune()
             self.assertIn(top_ctnr.id, report["ContainersDeleted"])

podman/tests/unit/test_container.py

@@ -101,6 +101,17 @@ def test_start(self, mock):
         container.start()
         self.assertTrue(adapter.called_once)
 
+    @requests_mock.Mocker()
+    def test_init(self, mock):
+        adapter = mock.post(
+            tests.LIBPOD_URL
+            + "/containers/87e1325c82424e49a00abdd4de08009eb76c7de8d228426a9b8af9318ced5ecd/init",
+            status_code=204,
+        )
+        container = Container(attrs=FIRST_CONTAINER, client=self.client.api)
+        container.init()
+        self.assertTrue(adapter.called_once)
+
     @requests_mock.Mocker()
     def test_stats(self, mock):
         stream = [