feat: only allow feedback once per version

Author: eug-vs

models/feedback/feedback.model.ts

@@ -1,5 +1,7 @@
 import { Model, model } from 'mongoose';
 import { FeedbackSchema, feedbackSchema } from './feedback.schema';
 
+feedbackSchema.index({ version: 1, authorId: 1 }, { unique: true }); // Unique together
+
 export default model<FeedbackSchema, Model<FeedbackSchema>>('Feedback', feedbackSchema);