Problem/Motivation
This is a follow up of #2828556: Display meaninguful error messages according to the link type.
The default HTML5 validation error for url input type is set by the browser, and most of them just display a message that does not really help the user to figure out how to correct an invalid link such as example.com, which is missing the protocol. In Firefox, the default validation error message is Please enter a URL.
Note: this validation is done only for LinkItemInterface::LINK_EXTERNAL, external links only.
Proposed resolution
Add a custom validation error message, such as Enter a full URL, such as http://example.com
Remaining tasks
Send patch
User interface changes
Changes the HTML5 validation error message for external links.
API changes
none
Data model changes
none
Screenshots
Default validation error message:
Custom validation error message: