Resolve "One letter domains in DNS filtered out by regex"

Closes #6108

See merge request ispconfig/ispconfig3!1445

Merge branch '6121-acme-sh-fails-when-self-signed-certificates-already-exist-for-ispconfig-web-interface' into 'develop'

Resolve "acme.sh fails when self-signed certificates already exist for ISPConfig web interface"

Closes #6121

See merge request ispconfig/ispconfig3!1494

Resolve "Mail Quota doesn't update on backup deletion"

Closes #6190

See merge request ispconfig/ispconfig3!1491

Resolve "IPv6 wildcard config missing in redirect server section"

Closes #6180

See merge request ispconfig/ispconfig3!1489

Resolve "clarify "ISPConfig v2 detected" message"

Closes #6198

See merge request ispconfig/ispconfig3!1498

Resolve "rspamd: enable arc signing"

Closes #6167

See merge request ispconfig/ispconfig3!1482

Resolve "deleting spamfilter_users should delete linked spamfilter_wblist"

Closes #6199

See merge request ispconfig/ispconfig3!1499

Update 500-backup_mail.inc.php Disable quota and ACLS when doing a backup of mdbox mailboxes with dsnyc

Resolve "Improve session security"

Closes #6179

See merge request !1488

Resolve "git-develop in ispconfig_update.sh not working"

Closes #6175

See merge request !1487

Resolve "Don't use password-protected keys for self-signed certificates"

Closes #6176

See merge request ispconfig/ispconfig3!1486

Resolve "Reverse search order for certbot and letsencrypt binary"

Closes #6172

See merge request ispconfig/ispconfig3!1485

Resolve "AWstats links"

Closes #6147

See merge request ispconfig/ispconfig3!1470

fixes #6084

Closes #6084

See merge request !1425

rspamd: fix remove-headers

See merge request ispconfig/ispconfig3!1483

Resolve "Update readme.md"

Closes #6160

See merge request ispconfig/ispconfig3!1481

#4961 modified remote API client edit to include lock and cancel, functions...

Closes #4961

See merge request ispconfig/ispconfig3!1453