Start implementation of model relations

src/util/support/types.ts

@@ -9,3 +9,12 @@ export type ParameterizedCallback<T> = ((arg: T) => any)
 
 /** A key-value form of a given type. */
 export type KeyValue<T> = {key: string, value: T}
+
+/** Simple helper method to verify that a key is a keyof some object. */
+export function isKeyof<T>(key: unknown, obj: T): key is keyof T {
+    if ( typeof key !== 'string' && typeof key !== 'symbol' ) {
+        return false
+    }
+
+    return key in obj
+}