Suggested changes to text string 'Only lowercase letters (a-z) and numbers are allowed'

[stillingen]

Hi.

The text string 'Only lowercase letters (a-z) and numbers are allowed' does not refer to which field it is related to. This can be a bit confusing for users are filling out fields when creating a new users. I would suggest to change the text so that it refers to the field it is relevant for, e.g: 'Username can only contain lowercase letters(a-z) and numbers, without space'

Code reference;
https://core.trac.wordpress.org/browser/trunk/src/wp-includes/ms-functions.php#L474
https://core.trac.wordpress.org/browser/trunk/src/wp-includes/ms-functions.php#L633

Since the text string both for user and site creation, this would also require a separate text string for site creation, E.g 'Sitename can only contain lowercase letters(a-z) and numbers, without space'

[atomicjack]

Changes the validation string for Username to make it obvious for which field it is assigned.

[atomicjack]

Missed a number off of the ticket ID - no actual code change from original patch

[bjornjohansen]

Improved first string, corrected second

[wonderboymusic]

I like this, thoughts?

[DrewAPicture]

We typically use username as one word, but otherwise, looks good.

[DrewAPicture]

Combined

[DrewAPicture]

In 35142:

Multisite: Improve two error strings specifying allowed characters in usernames and site names.

Also removes two error strings that were likely never being triggered anyway due to the stricter character matching higher up.

Props atomicjack, bjornjohansen, DrewAPicture.
Fixes #33336.