Merge #2641

2641: Remove webmail cookies on logout. r=mergify[bot] a=ghostwheel42

## What type of PR?

bug-fix

## What does this PR do?

sometimes at least roundcube webmail is confused when changing users.
this deletes the webmail session cookies to avoid the confusion.


Co-authored-by: Alexander Graf <ghostwheel42@users.noreply.github.com>

core/admin/mailu/sso/views/base.py

@@ -57,7 +57,10 @@ def login():
 def logout():
     flask_login.logout_user()
     flask.session.destroy()
-    return flask.redirect(flask.url_for('.login'))
+    response = flask.redirect(flask.url_for('.login'))
+    for cookie in ['roundcube_sessauth', 'roundcube_sessid', 'smsession']:
+        response.set_cookie(cookie, 'empty', expires=0)
+    return response
 
 
 @sso.route('/proxy', methods=['GET'])