@Alpha
    default Collection<ExtensionHandlerFactory> getExtensionHandlerFactories(ConfigRegistry config) {
        return Collections.emptySet();
    }
Returns a collection of {@link ExtensionHandlerFactory} objects. These factories are used in
addition to the factories that have been registered with {@link Extensions#registerHandlerFactory}.
<br>
Handler factories returned here can customize the behavior of the Extension factory itself.

@param config A Configuration registry object that can be used to look up additional information
@return A collection of {@link ExtensionHandlerFactory} objects. Can be empty, must not be null

@since 3.38.0
core/src/main/java/org/jdbi/v3/core/extension/ExtensionFactory.java