LPS-50299 validate kbArticle urlTitle

If the urlTitle is given explicitly, don't surprise the user by changing
it if it is a duplicate.
LPS-50299 remove trailing slash from user input

Code expects that the urlTitle stored in the database has no leading
slash.
LPS-50299 add error message to the view
LPS-50299 autogenerated
LPS-50299 Adapt language keys to follow the same pattern as in portal
LPS-50299 SF
LPS-50299 lang keys