v2.3.0

misc: Allow setting init_containers with null condition @adamantike (#289)

## what

This change allows configuring init_containers that are not added to the depends_on list for the main container, by setting null as the container condition.

why

This is useful for containers that actually depend on the main container, and not the other way around. For example, a nginx sidecar that needs to wait for the main container to be healthy before starting.

By allowing null as the container condition, this is a non-breaking change.