feat: Implement initial version of getExecutions query

packages/backend/src/models/flow.ts

@@ -1,6 +1,7 @@
 import { ValidationError } from 'objection';
 import Base from './base';
 import Step from './step';
+import Execution from './execution';
 
 class Flow extends Base {
   id!: string;
@@ -31,6 +32,14 @@ class Flow extends Base {
         to: 'steps.flow_id',
       },
     },
+    executions: {
+      relation: Base.HasManyRelation,
+      modelClass: Execution,
+      join: {
+        from: 'flows.id',
+        to: 'executions.flow_id',
+      },
+    },
   });
 
   async $beforeUpdate(): Promise<void> {