feat: link and unlink document to resource model

packages/server/src/models/DocumentLink.ts

@@ -0,0 +1,44 @@
+import { Model, mixin } from 'objection';
+import TenantModel from 'models/TenantModel';
+import ModelSetting from './ModelSetting';
+import ModelSearchable from './ModelSearchable';
+
+export default class DocumentLink extends mixin(TenantModel, [
+  ModelSetting,
+  ModelSearchable,
+]) {
+  /**
+   * Table name
+   */
+  static get tableName() {
+    return 'document_links';
+  }
+
+  /**
+   * Model timestamps.
+   */
+  get timestamps() {
+    return ['createdAt', 'updatedAt'];
+  }
+
+  /**
+   * Relationship mapping.
+   */
+  static get relationMappings() {
+    const Document = require('models/Document');
+
+    return {
+      /**
+       * Sale invoice associated entries.
+       */
+      document: {
+        relation: Model.HasOneRelation,
+        modelClass: Document.default,
+        join: {
+          from: 'document_links.documentId',
+          to: 'documents.id',
+        },
+      },
+    };
+  }
+}