Feature #4566: pgsql: add subprotocol-states
pgsql: Add COPY subprotocol-state
When the postgresql backend sends or receives the following commands:
- "COPY FROM STDIN"
- "COPY TO STDOUT"
It enters the COPY subprotocol-state, which comprises a different set of messages.
Currently, if Suri has the pgsql app-layer enabled and sees one of those messages, it doesn't know what to do and stops parsing pgsql messages from that flow altogether, afterwards.
PostgreSQL documentation: https://www.postgresql.org/docs/14/protocol-flow.html#PROTOCOL-COPY