attachment create: support pulling relevant compression option defaults from the config

[radhermit]

It could be useful to be able to override the default compression type via config option without having to specify an explicit compression type in the related --compress <type> option for every call.

This would probably require collapsing the type argument to a enum value while running instead of internally via clap parsing since the config object wouldn't be available in that context.

[radhermit]

Also, being able to set defaults for --auto-compress and --auto-truncate per connection could be useful as well since the default setup with mariadb/mysql limits it to 1Mb.