feat: rewrite repositories with base entity repository class.

feat: sales and purchases status.
feat: sales and purchases auto-increment number.
fix: settings find query with extra columns.

server/src/models/Customer.js

@@ -0,0 +1,78 @@
+import { Model, QueryBuilder } from 'objection';
+import TenantModel from 'models/TenantModel';
+
+
+class CustomerQueryBuilder extends QueryBuilder {
+  constructor(...args) {
+    super(...args);
+
+    this.onBuild((builder) => {
+      if (builder.isFind() || builder.isDelete() || builder.isUpdate()) {
+        builder.where('contact_service', 'customer');
+      }
+    });
+  }
+}
+
+export default class Customer extends TenantModel {
+  /**
+   * Query builder.
+   */
+  static get QueryBuilder() {
+    return CustomerQueryBuilder;
+  }
+
+  /**
+   * Table name
+   */
+  static get tableName() {
+    return 'contacts';
+  }
+
+  /**
+   * Model timestamps.
+   */
+  get timestamps() {
+    return ['createdAt', 'updatedAt'];
+  }
+
+  /**
+   * Defined virtual attributes.
+   */
+  static get virtualAttributes() {
+    return ['closingBalance'];
+  }
+
+  /**
+   * Closing balance attribute.
+   */
+  get closingBalance() {
+    return this.openingBalance + this.balance;
+  }
+
+  /**
+   * Relationship mapping.
+   */
+  static get relationMappings() {
+    const SaleInvoice = require('models/SaleInvoice');
+
+    return {
+      salesInvoices: {
+        relation: Model.HasManyRelation,
+        modelClass: SaleInvoice.default,
+        join: {
+          from: 'contacts.id',
+          to: 'sales_invoices.customerId',
+        },
+      },
+    };
+  }
+
+  static get fields() {
+    return {
+      created_at: {
+        column: 'created_at',
+      }
+    };
+  }
+}