Function validate_repository_replication_admission_extras 

pub fn validate_repository_replication_admission_extras(
    spec: &RepositoryReplicationSpec,
) -> Vec<ValidationError>

Admission-only extras for a RepositoryReplication: parse AND bound the schedule jitter. Same history as Maintenance — validate_repository_replication checks the cron and timezone but never the jitter, so both halves are new rejections over a field stored objects already carry.