feat: Implement get flow API endpoint

packages/backend/src/controllers/api/v1/flows/get-flow.js

@@ -0,0 +1,11 @@
+import { renderObject } from '../../../../helpers/renderer.js';
+
+export default async (request, response) => {
+  const flow = await request.currentUser.authorizedFlows
+    .withGraphJoined({ steps: true })
+    .orderBy('steps.position', 'asc')
+    .findOne({ 'flows.id': request.params.flowId })
+    .throwIfNotFound();
+
+  renderObject(response, flow);
+};