Logout URL is incorrect.

Problem/Motivation

It seems that the $logout_url variable in following line is getting a wrong value by calling getLoginUrl().

 $logout_url = parse_url($this_idp->getLoginUrl());
 $logout_url = $logout_url['scheme'] . '://' . $logout_url['host'];

Should it call getLogoutUrl() instead?

See
https://git.drupalcode.org/project/saml_sp/-/blob/4.2.1/modules/saml_sp_...

Proposed resolution

Replace follow line

 $logout_url = parse_url($this_idp->getLoginUrl());
 $logout_url = $logout_url['scheme'] . '://' . $logout_url['host'];

With:

 $logout_url = parse_url($this_idp->getLogoutUrl());
 $logout_url = $logout_url['scheme'] . '://' . $logout_url['host'];

Remaining tasks

Test to confirm.