Squashed commit of the following:

commit 402759bd
Author: Herman van Rink <rink@initfour.nl>
Date:   Sun Jul 23 23:19:27 2023 +0200

    Add language_error_empty to the language files, #6495

    In addition to !1719

commit 4bb60f20
Author: Herman van Rink <rink@initfour.nl>
Date:   Tue Jul 4 23:12:23 2023 +0200

    Use DMARC form to edit DMARC records, #6387

commit b8929250
Author: Johannes Koschier <hannes@cheat.at>
Date:   Wed Jun 7 09:35:53 2023 +0000

    6521_database_list_sort_on_dbuser_column

commit 2513df3f
Author: Herman van Rink <rink@initfour.nl>
Date:   Sun Jul 23 21:39:28 2023 +0200

    Fix sorting of the database list by user, #6521

commit 8fe6d116
Author: Herman van Rink <rink@initfour.nl>
Date:   Sun Jul 23 17:26:39 2023 +0200

    Rewrite to improve readability

commit dfdab8a1
Author: Herman van Rink <rink@initfour.nl>
Date:   Tue Jul 4 21:55:12 2023 +0200

    Better detect an existing spf record, #6537

    '' and 'example.com.' are effectively the same.

commit 713b6221
Author: Herman van Rink <rink@initfour.nl>
Date:   Tue Jul 4 21:54:47 2023 +0200

    Initialize new SPF record to have a hostname, #6537

Resolve "Dashboard Limit shows MB of Unlimited"

Closes #6544

See merge request ispconfig/ispconfig3!1772

Resolve "Account limit incorrectly informed in dashboard - ISPConfig 3.2.10"

Closes #6528

See merge request ispconfig/ispconfig3!1771

Merge branch '6533-domain-module-prevents-subdomains-to-be-added-for-domains-that-exist-as-website' into 'develop'

Resolve "Domain module prevents subdomains to be added for domains that exist as website"

Closes #6533

See merge request ispconfig/ispconfig3!1770

Enable DKIM when generating a Private-key #6538

See merge request ispconfig/ispconfig3!1766

Merge branch '6533-domain-module-prevents-subdomains-to-be-added-for-domains-that-exist-as-website' into 'develop'

Resolve "Domain module prevents subdomains to be added for domains that exist as website"

Closes #6533

See merge request ispconfig/ispconfig3!1764

Resolve "DNS Zone list server column empty"

Closes #6524

See merge request ispconfig/ispconfig3!1760

Resolve "API dkim_selector_error in mail_domain_add ()"

Closes #6523

See merge request ispconfig/ispconfig3!1759

Resolve "DNS Wizard not working with use_domain_module = y"

Closes #6519

See merge request ispconfig/ispconfig3!1758

Merge branch '6522-dns-zones-can-not-be-added-with-wizard-when-domain-module-is-enabled' into 'develop'

Resolve "DNS zones can not be added with Wizard when domain module is enabled."

Closes #6522

See merge request ispconfig/ispconfig3!1757

Replace one more occurance of slave_zone_file_prefix, #6520

See merge request ispconfig/ispconfig3!1755

Fix mixed up version numbers in check_mysql_version

See merge request ispconfig/ispconfig3!1750

Improve verbosity when an error occurs during replication

Closes #6510

See merge request ispconfig/ispconfig3!1747

Only display a dashlet table if there is content for it, #6512

See merge request !1749

6516_help_system_message_sort_fix

See merge request ispconfig/ispconfig3!1752

Resolve "Error sending support message in ISPConfig panel"

Closes #6515

See merge request ispconfig/ispconfig3!1751