Function extract_schema_id 

pub(crate) fn extract_schema_id(
    payload: &[u8],
) -> Result<(i32, &[u8]), WireFormatError>

Returns (schema_id, payload)

Refer to Confluent schema registry wire format

Bytes	Area	Description
0	Magic Byte	Confluent serialization format version number; currently always 0.
1-4	Schema ID	4-byte schema ID as returned by Schema Registry.
5-…	Data	Serialized data for the specified schema format (for example, binary encoding for Avro or Protobuf.