Fix bug 366 (#764)

* Optimize DB

* Clean up names

* fixup! Clean up names

* fixup! fixup! Clean up names

backend/shared/database/BaseRepository.js

@@ -0,0 +1,46 @@
+'use strict';
+
+/**
+ * Base repository class providing common data access methods.
+ * Extend this class to create entity-specific repositories.
+ */
+class BaseRepository {
+    constructor(model) {
+        this.model = model;
+    }
+
+    async findById(id, options = {}) {
+        return this.model.findByPk(id, options);
+    }
+
+    async findOne(where, options = {}) {
+        return this.model.findOne({ where, ...options });
+    }
+
+    async findAll(where = {}, options = {}) {
+        return this.model.findAll({ where, ...options });
+    }
+
+    async create(data, options = {}) {
+        return this.model.create(data, options);
+    }
+
+    async update(instance, data, options = {}) {
+        return instance.update(data, options);
+    }
+
+    async destroy(instance, options = {}) {
+        return instance.destroy(options);
+    }
+
+    async count(where = {}, options = {}) {
+        return this.model.count({ where, ...options });
+    }
+
+    async exists(where) {
+        const count = await this.count(where);
+        return count > 0;
+    }
+}
+
+module.exports = BaseRepository;