public Builder addExtensionHandlerCustomizer(ExtensionHandlerCustomizer extensionHandlerCustomizer) {
            this.extensionHandlerCustomizers.add(extensionHandlerCustomizer);
            return this;
        }
Adds an {@link ExtensionHandlerCustomizer} that will be used to customize extension handlers when the {@link Builder#build()}} method is called.
@param extensionHandlerCustomizer An {@link ExtensionHandlerCustomizer} instance
@return The builder instance
core/src/main/java/org/jdbi/v3/core/extension/ExtensionMetadata.java