Function rocksdb_backup_engine_create_new_backup_with_metadata 

pub unsafe extern "C" fn rocksdb_backup_engine_create_new_backup_with_metadata(
    be: *mut rocksdb_backup_engine_t,
    db: *mut rocksdb_t,
    options: *const rocksdb_create_backup_options_t,
    app_metadata: *const c_char,
    app_metadata_len: usize,
    backup_id: *mut u32,
    errptr: *mut *mut c_char,
)