Show in the legend when a remote data layer failed to load #2936
Description
When a layer fails to load there is already a red pop-up that shows up, with the full URL of the failed endpoint.
But I think that's not quite user-friendly, especially for non-technical persons.
My suggestion would be to add an icon in the legend, next to the layer that failed to load. For example a classic "exclamation mark in a circle" like https://commons.wikimedia.org/wiki/File:Exclamation_Circle_Red.svg
When hovering the mouse on the icon (or clicking) a more detailed message could show up like "Failed to load remote data from XXX"
What do you think ?