explain v31 db row format warning

[meonkeys]

☑️ Resolves

There is no associated issue, just this PR.

🖼️ Screenshots

[susnux]

Suggested change

	We have a new setup warning for MySQL and MariaDB databases if any tables are using a row format other than Dynamic.
	This is likely true for older installations.
	To resolve the warning, issue the proper ``ALTER TABLE`` DDL commands to change the row format during a maintenance window.
	If you're not sure how to do this, you can `find some tips and tricks from the community <https://help.nextcloud.com/t/upgrade-to-nextcloud-hub-10-31-0-0-incorrect-row-format-found-in-your-database/218366/>`_.
	Other row formats than ``DYNAMIC`` for MySQL and MariaDB databases will issue a warning since Nextcloud 24,
	as they often cause performance issues.
	With Nextcloud 31 a more prominent new setup warning for this was added.
	To resolve the warning, in most cases running ``occ db:convert-mysql-charset`` will resolve the issue.
	If some tables are not covered by the ``occ`` command, issuing the proper ``ALTER TABLE`` DDL commands to change the row format during a maintenance window is needed.
	If you're not sure how to do this, you can `find some tips and tricks from the community <https://help.nextcloud.com/t/upgrade-to-nextcloud-hub-10-31-0-0-incorrect-row-format-found-in-your-database/218366/>`_.

Maybe something like this as its not a random setup warning but already a warning since Nextcloud 24 and based on performance issues.
Also the occ command is in most cases much simpler than custom scripts.

[meonkeys]

Thank you you @susnux ! Where did the warning appear before v31? It looks like it was added just recently. Oh never mind, I see it was the default for new installs, but yes, we just added the warning.

And thanks for mentioning that occ command, I didn't know about that.

I think I'll accept your suggestion and modify it slightly.

[susnux]

"Missing documentation" of nextcloud/server#48547

[susnux]

@meonkeys thank you for your pull request!

[susnux]

/backport to stable31

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