Macro impl_blob_codec 

macro_rules! impl_blob_codec {
    ($($t:ty),+ $(,)?) => { ... };
}

Generates ToSqlValue and FromSqlValue for types stored as a BLOB via their Serializable/Deserializable impls.

The generated impls call the exact same to_bytes()/read_from_bytes() used elsewhere, so the on-disk byte layout is unchanged.