nixos/nextcloud: temp fix for MariaDB >=10.6

The MariaDB version 10.6 doesn't seem supported with current Nextcloud
versions and the test fails with the following error[1]:

    nextcloud # [   14.950034] nextcloud-setup-start[1001]: Error while trying to initialise the database: An exception occurred while executing a query: SQLSTATE[HY000]: General error: 4047 InnoDB refuses to write tables with ROW_FORMAT=COMPRESSED or KEY_BLOCK_SIZE.

According to a support-thread in upstream's Discourse[2] this is because
of a missing support so far.

Considering that we haven't received any bugreports so far - even though
the issue already exists on master - and the workaround[3] appears to
work fine, an evaluation warning for administrators should be
sufficient.

[1] https://hydra.nixos.org/build/155015223
[2] https://help.nextcloud.com/t/update-to-next-cloud-21-0-2-has-get-an-error/117028/15
[3] setting `innodb_read_only_compressed=0`

(cherry picked from commit 675e262f5a03eb9aa6b0500434ee30a9d6b882a0)

nixos/tests/nextcloud/with-mysql-and-memcached.nix

@@ -39,6 +39,13 @@ in {
         enable = true;
         bind = "127.0.0.1";
         package = pkgs.mariadb;
+
+        # FIXME(@Ma27) Nextcloud isn't compatible with mariadb 10.6,
+        # this is a workaround.
+        # See https://help.nextcloud.com/t/update-to-next-cloud-21-0-2-has-get-an-error/117028/22
+        extraOptions = ''
+          innodb_read_only_compressed=0
+        '';
         initialScript = pkgs.writeText "mysql-init" ''
           CREATE USER 'nextcloud'@'localhost' IDENTIFIED BY 'hunter2';
           CREATE DATABASE IF NOT EXISTS nextcloud;