Docker configuration fixes

[federico-razzoli]

Fixes in the configuration file:

• Remove deprecated innodb_file_per_table
• Split [client] and [mariadb-client] because default_character_set is not understood by some clients
• Use default_character_set with underscore instead of dashes for consistence

[guycipher]

@federico-razzoli the contributor agreement is failing. Could you approve it? The PR looks good

[guycipher]

@federico-razzoli do you have a reference on that config being deprecated and potentially what versions

[guycipher]

"When innodb_file_per_table=ON is set, InnoDB uses one tablespace file per InnoDB table. These tablespace files have the .ibd extension. When innodb_file_per_table=OFF is set, InnoDB stores all tables in the InnoDB system tablespace.
InnoDB versions in MySQL 5.7 and above also support an additional type of tablespace called general tablespaces that are created with CREATE TABLESPACE. However, InnoDB versions in MariaDB Server do not support general tablespaces or CREATE TABLESPACE."

https://mariadb.com/docs/server/server-usage/storage-engines/innodb/innodb-tablespaces/innodb-file-per-table-tablespaces

[federico-razzoli]

@guycipher It's deprecated since 11.0. Since MariaDB's first version, the default is 1.

When a variable is deprecated, you can see it in the documentation and in the error log.

Documentation:

https://mariadb.com/docs/server/server-usage/storage-engines/innodb/innodb-system-variables#innodb_file_per_table

Error log:

2026-04-10 12:14:06 0 [Warning] --innodb-file-per-table is deprecated and will be removed in a future release

[federico-razzoli]

For some reason this PR doesn't contain a change I thought it would contain. I need to re-add it.

[federico-razzoli]

Re-applied lost change and signed off.

[guycipher]

The charset there per research is the default anyways in MariaDB v10+.