Consider overriding configuration instead of replacing the default ones

[AntonFriberg]

Hi!

According to the ClickHouse Tutorial and recommendation from users in the Telegram channel, one should not replace the default configuration but instead override the config by placing them under config.d directory or users.d instead.

If you want to adjust the configuration, it’s not handy to directly edit config.xml file, considering it might get rewritten on future package updates. The recommended way to override the config elements is to create files in config.d directory which serve as “patches” to config.xml.

https://clickhouse.com/docs/en/getting-started/tutorial/#clickhouse-tutorial

The resulting configuration of all system settings and user settings can be seen in /var/lib/clickhouse/preprocessed_configs/config.xml and /var/lib/clickhouse/preprocessed_configs/users.xml which is useful during debugging.

I tried making a small change in https://github.com/AlexeySetevoi/ansible-clickhouse/blob/master/tasks/configure/sys.yml that seems to work as expected.

 - name: Config | Generate system config
   template:
     src: config.j2
-     dest: "{{ clickhouse_path_configdir }}/config.xml"
+     dest: "{{ clickhouse_path_configdir }}/config.d/config.xml"

 - name: Config | Generate users config
   template:
     src: users.j2
-     dest: "{{ clickhouse_path_configdir }}/users.xml"
+     dest: "{{ clickhouse_path_configdir }}/users.d/users.xml"

Additionally, I think it is better if we move the conf.d configuration to config.d since then it will not be included in /var/lib/clickhouse/preprocessed_configs/users.xml and only in /var/lib/clickhouse/preprocessed_configs/config.xml

I could provide a PR with the changes so that you can try it if you want?