feat: add workflows table & service

invokeai/app/api/routers/workflows.py

@@ -0,0 +1,20 @@
+from fastapi import APIRouter, Body, Path
+
+from invokeai.app.api.dependencies import ApiDependencies
+from invokeai.app.services.workflow_records.workflow_records_common import WorkflowField
+
+workflows_router = APIRouter(prefix="/v1/workflows", tags=["workflows"])
+
+
+@workflows_router.get(
+    "/i/{workflow_id}",
+    operation_id="get_workflow",
+    responses={
+        200: {"model": WorkflowField},
+    },
+)
+async def get_workflow(
+    workflow_id: str = Path(description="The workflow to get"),
+) -> WorkflowField:
+    """Gets a workflow"""
+    return ApiDependencies.invoker.services.workflow_records.get(workflow_id)