Function write_header_with_epoch 

pub fn write_header_with_epoch(
    data: &mut [u8],
    disc: u8,
    version: u8,
    layout_id: &[u8; 8],
    schema_epoch: u32,
) -> ProgramResult

Write a Hopper header with a caller-specified schema epoch.

Used by migration helpers that need to stamp a new epoch while preserving disc/version/layout_id. Regular account creation should go through write_header (which defaults the epoch to 1) or init_header.