fix: Adjust null flag for step model fields

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

@@ -44,6 +44,7 @@ const createStepResolver = async (
     appKey: input.appKey,
     type: StepEnumType.Action,
     position: previousStep.position + 1,
+    parameters: {},
   });
 
   const nextSteps = await flow

packages/backend/src/models/step.ts

@@ -27,13 +27,13 @@ class Step extends Base {
     properties: {
       id: { type: 'integer' },
       flowId: { type: 'string' },
-      key: { type: ['string', null] },
-      appKey: { type: ['string', null], minLength: 1, maxLength: 255 },
+      key: { type: ['string', 'null'] },
+      appKey: { type: ['string', 'null'], minLength: 1, maxLength: 255 },
       type: { type: 'string', enum: ['action', 'trigger'] },
-      connectionId: { type: ['string', null] },
+      connectionId: { type: ['string', 'null'] },
       status: { type: 'string', enum: ['incomplete', 'completed'] },
       position: { type: 'integer' },
-      parameters: { type: ['object', null] },
+      parameters: { type: 'object' },
     },
   };