Function bind_state_body_to_mutation 

pub fn bind_state_body_to_mutation<M>(
    descriptor: &DomainEventDescriptor,
    program: MutationProgram,
    input_root: &str,
) -> Result<ProjectionHandler, MutationProgramError>
where
    M: RelationalReadModel,

Spec: projection arm — domain-event body → mutation input object.

When the event fires, every non-skipped model column is bound from the event body into input.{input_root}.{field}.

Errors

Propagates selector or binding construction failures.