feat: Create flow model and graphQL mutation

packages/backend/src/graphql/mutations/create-flow.ts

@@ -0,0 +1,18 @@
+import Flow from '../../models/flow';
+import flowType from '../types/flow';
+import RequestWithCurrentUser from '../../types/express/request-with-current-user';
+
+const createFlowResolver = async (req: RequestWithCurrentUser) => {
+  const flow = await Flow.query().insert({
+    userId: req.currentUser.id
+  });
+
+  return flow;
+}
+
+const createFlow = {
+  type: flowType,
+  resolve: (_: any, _params: any, req: RequestWithCurrentUser) => createFlowResolver(req)
+};
+
+export default createFlow;