Add user config model for future usage

src/models/userConfig.ts

@@ -0,0 +1,20 @@
+import mongoose from 'mongoose';
+
+const userConfigSchema = new mongoose.Schema({
+	authorID: {
+		type: String,
+		required: true,
+	},
+	subjects: {
+		type: [String],
+		required: false,
+		default: null,
+	},
+	gradeLevels: {
+		type: [String],
+		required: false,
+		default: null,
+	},
+});
+
+export default mongoose.model('UserConfig', userConfigSchema);