chore: Typescript database models (#2886)

closes #2798

server/models/decorators/Fix.ts

@@ -0,0 +1,50 @@
+/**
+ * A decorator that must be applied to every model definition to workaround
+ * babel <> typescript incompatibility. See the following issue:
+ * https://github.com/RobinBuschmann/sequelize-typescript/issues/612#issuecomment-491890977
+ *
+ * @param target model class
+ */
+
+export default function Fix(target: any): void {
+  return class extends target {
+    constructor(...args: any[]) {
+      super(...args);
+
+      const rawAttributes = Object.keys(new.target.rawAttributes);
+      const associations = Object.keys(new.target.associations);
+
+      rawAttributes.forEach((propertyKey) => {
+        // check if we already defined getter/setter – if so, do not override
+        const desc = Object.getOwnPropertyDescriptor(
+          target.prototype,
+          propertyKey
+        );
+        if (desc) {
+          return;
+        }
+
+        Object.defineProperty(this, propertyKey, {
+          get() {
+            return this.getDataValue(propertyKey);
+          },
+          set(value) {
+            this.setDataValue(propertyKey, value);
+          },
+        });
+      });
+
+      associations.forEach((propertyKey) => {
+        Object.defineProperty(this, propertyKey, {
+          get() {
+            return this.dataValues[propertyKey];
+          },
+          set(value) {
+            // sets without changing the "changed" flag for associations
+            this.dataValues[propertyKey] = value;
+          },
+        });
+      });
+    }
+  } as any;
+}