Ability to change Message

I've added a config form for plugging in your custom message. You can find it at /admin/config/allow_only_one/settings.

Apply the patch and let me know if it works fine.

hi #sidharth_soman,
First of all - thank you for your effort and help, much appreciated.

I just tested and everything works as expected.

Thanks for the feedback!

It just occurred to me that it would be more useful to add a menu link under the configuration tab in the toolbar so that the user can access the form through the UI. I'm attaching a patch for it.

Thank you, make sense. And not sure if it is is too difficult to implement but message for bundle would be also fine so there is a different one for other conent types or taxonomies, but not necessary.