Added docstrings about override in the router and error handlers as well

Author: sdangol

packages/event-handler/src/rest/ErrorHandlerRegistry.ts

@@ -76,6 +76,8 @@ export class ErrorHandlerRegistry {
    * Merges another {@link ErrorHandlerRegistry | `ErrorHandlerRegistry`} instance into the current instance.
    * It takes the handlers from the provided registry and adds them to the current registry.
    *
+   * Error handlers from the included router are merged with existing handlers. If handlers for the same error type exist in both routers, the included router's handler takes precedence.
+   *
    * @param errorHandlerRegistry - The registry instance to merge with the current instance
    */
   public merge(errorHandlerRegistry: ErrorHandlerRegistry): void {

packages/event-handler/src/rest/RouteHandlerRegistry.ts

@@ -202,6 +202,8 @@ class RouteHandlerRegistry {
    * Merges another {@link RouteHandlerRegistry | `RouteHandlerRegistry`} instance into the current instance.
    * It takes the static and dynamic routes from the provided registry and adds them to the current registry.
    *
+   * Routes from the included router are added to the current router's registry. If a route with the same method and path already exists, the included router's route takes precedence.
+   *
    * @param routeHandlerRegistry - The registry instance to merge with the current instance
    * @param options - Configuration options for merging the router
    * @param options.prefix - An optional prefix to be added to the paths defined in the router