Add table schema version in package

What does this MR do?

This MR adds a VersionHash field to the LogicalReplicationEvents protobuf message. The VersionHash is a fingerprint that represents the specific state of a database table's schema at the time an event package was generated.

Key Changes

1. Protobuf Update: Added uint64 version_hash field to LogicalReplicationEvents message

2. Schema Version Calculation: Implemented hash calculation based on:

   • Table name and schema
   • Column names and their data types (sorted alphabetically)
   • Uses XXH3 algorithm for hashing

3. Queue Interface Changes: Updated PersistentQueue.Add() method signature to accept RelationMessageWithVersion instead of separate table/schema parameters, enabling version hash propagation

4. Consumer Updates:

   • Demo consumer now displays the version hash
   • All queue implementations (NATS, Noop) updated to include version hash in events

5. Documentation: Added comprehensive section in README explaining:

   • What VersionHash is and why it's useful
   • How to use it for detecting schema drift
   • How the hash is calculated
   • SQL query to compute the hash for verification

How do I test it?

You can test the behavior using the simulator:

cd simulator
docker compose up --build

See the logs for the demo consumer:

docker compose logs  | grep siphon_consumer_1_demo

You should see the version hash printed for the users package:

siphon_consumer_1_demo  | Application identifier:  siphon-producer-db1
siphon_consumer_1_demo  | PostgreSQL table:  users
siphon_consumer_1_demo  | PostgreSQL schema:  public
siphon_consumer_1_demo  | PostgreSQL table schema version hash:  17321062187436956279

Start psql and update some rows to trigger another package:

psql "host=localhost port=5433 user=db1 password=db1 dbname=siphon"

update users set updated_at=now();

You should see a new entry in the logs with the same version hash:

siphon_consumer_1_demo  | Application identifier:  siphon-producer-db1
siphon_consumer_1_demo  | PostgreSQL table:  users
siphon_consumer_1_demo  | PostgreSQL schema:  public
siphon_consumer_1_demo  | PostgreSQL table schema version hash:  17321062187436956279
siphon_consumer_1_demo  | Event count:  3
siphon_consumer_1_demo  | First event:  operation:OPERATION_UPDATE  columns:{column_index:2  value:{int64_value:1}}  columns:{column_index:3  value:{string_value:"User Name1"}}  columns:{column_index:5  value:{string_value:"user1"}}  columns:{value:{string_value:"about"}}  columns:{column_index:1  value:{timestamp_value:{seconds:1765471970  nanos:303107}}}  columns:{column_index:4  value:{timestamp_value:{seconds:1765472071  nanos:265503}}}

Make a change to the PostgreSQL DB schema:

ALTER TABLE users ADD COLUMN foo bigint;
-- update some rows
update users set updated_at=now();

The version hash in the output should change:

siphon_consumer_1_demo  | Application identifier:  siphon-producer-db1
siphon_consumer_1_demo  | PostgreSQL table:  users
siphon_consumer_1_demo  | PostgreSQL schema:  public
siphon_consumer_1_demo  | PostgreSQL table schema version hash:  8784686533527315965