feat: add metric service create api

Signed-off-by: ImMin5 <[email protected]>

src/spaceone/inventory_v2/interface/grpc/__init__.py

@@ -3,6 +3,7 @@
 from .collector import Collector
 from .job import Job
 from .job_task import JobTask
+from .metric import Metric
 from .namespace_group import NamespaceGroup
 from .namespace import Namespace
 from .metric import Metric