Check if ISPConfig is configured with NGINX or with Apache instead of installed software (Fixes #26290)

Added admin IP whitelist feature

See merge request ispconfig/ispconfig3!1544

Add API event support to mail_domain_*, mail_user_*, mail_alias_*, mail_forward_*

See merge request ispconfig/ispconfig3!1394

Changed hardcoded quota warning levels to be adjustable in server config

Closes #1096

See merge request ispconfig/ispconfig3!1545

Show rendered bind dns zone in extra tab

See merge request ispconfig/ispconfig3!1379

Resolve "mail transport + @domain relay recipient = open relay"

Closes #6218

See merge request ispconfig/ispconfig3!1511

Add slovak translation for templates

Closes #6265

See merge request !1550

Merge branch '6269-redirects-render-invalid-apache-config-on-non-ssl-web-server-since-mr-1521-jdsn' into 'develop'

Only add SSLProxyEngine in proxy mode and when SSL is enabled for the web (fixes #6269)

Closes #6269

See merge request ispconfig/ispconfig3!1549

Create symlinks for conveniance, SFTP user should not land in an empty dir.

Closes #6240

See merge request !1529

Resolve "letsencrypt_renew_hook.sh error restarting services on centos"

Closes #6255

See merge request ispconfig/ispconfig3!1542

6187-DS-RECORD-functions-for-API -> Update dns.inc.php and other related files

Closes #6187

See merge request !1493

Add ipv6 option for dns_templatezone_add()

Closes #6239

See merge request ispconfig/ispconfig3!1528

Update jk_init.ini.master: add php8.1

See merge request ispconfig/ispconfig3!1547

Dsync backup: global options must be placed before the actual command

Closes #6243

See merge request ispconfig/ispconfig3!1532

Merge branch '5889-place-reject_rbl_client-after-permit_sasl_authenticated-in-postfix-config' into 'develop'

Resolve "Place reject_rbl_client after permit_sasl_authenticated in postfix config"

Closes #5889

See merge request ispconfig/ispconfig3!1531

SSLProxyEngine is neither needed for http(s) redirects nor for non-SSL proxy configs.
Thus excluding it from these cases.

Based on a fix by Thom <thom@amsterdamtech.nl>

Refactor: Extracted some common code as include_menu_dir_files() method in a new file named common.php.