confluence plugin wrongly hint to try `kinit` when `auth_url` lead to a non existent page

[sandrobonazzola]

Spent some time today trying to understand what was wrong with kerberos trying to get report for confluence pages as I got error Confluence authentication failed. Try kinit. on the screen.
It sorted out that the default auth_url was pointing to {url}/step-auth-gss which lead to 404 on this specific confluence instance.
I still need to figure out the right auth_url for this instance but the error here could be more helpful.