kiwibuild: Allow setting metadata type explicitly

It is not possible to reliably detect what the type for an image should
be in the metadata. This commit adds an option for user to explicitly
provide it.

It can only be configured on the specific image, not globally.

Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>

tests/test_kiwibuildphase.py

@@ -73,6 +73,7 @@ class TestKiwiBuildPhase(PungiTestCase):
                 "bundle_name_format": "fmt",
                 "version": "Rawhide",
                 "repo_releasever": "41",
+                "manifest_type": "live-kiwi",
             },
             MINIMAL_CONF,
         )
@@ -366,7 +367,9 @@ class TestKiwiBuildThread(PungiTestCase):
                 "kiwibuild_bundle_format": "%N-%P-40_Beta-%I.%A.%T",
             },
         )
-        config = _merge({"subvariant": "Test"}, MINIMAL_CONF)
+        config = _merge(
+            {"subvariant": "Test", "manifest_type": "live-kiwi"}, MINIMAL_CONF
+        )
         pool = mock.Mock()
 
         get_image_paths = KojiWrapper.return_value.get_image_paths
@@ -459,7 +462,7 @@ class TestKiwiBuildThread(PungiTestCase):
             assert kwargs["arch"] == image.arch
             assert image.path == expected_path
             assert "iso" == image.format
-            assert "iso" == image.type
+            assert "live-kiwi" == image.type
             assert image.bootable
             assert "Test" == image.subvariant