@Nullable
    default String guessServiceName(Object exampleRequest) {
        return null;
    }
Guesses the name of the service who handles the specified example request.

@param exampleRequest the example request object which is an instance of one of the {@link Class}es
                      returned by {@link #supportedExampleRequestTypes()}

@return the service name, or {@code null} if failed to guess.
core/src/main/java/com/linecorp/armeria/server/docs/DocServicePlugin.java