CMS-46358 Add string type to PropertyGroupKey for enhanced flexibility and refactor code.

Author: TRomesh

packages/optimizely-cms-cli/src/service/propertyGroups.ts

@@ -26,4 +26,5 @@ export interface PropertyGroupRegistry {
 // Type that combines built-in groups, registered custom groups
 export type PropertyGroupKey =
   | BuiltInPropertyGroups
-  | keyof PropertyGroupRegistry;
+  | keyof PropertyGroupRegistry
+  | (string & {});