Issue171 snapshot serialization

[rafalpiotrowski]

Fixes #171
applied the same logic when serializing snapshot as in journal when it comes to setting manifest

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[Aaronontheweb]

cc @CumpsD @Arkatufus

[CumpsD]

Pasting this here for reference what to compare to:

        protected override void WriteEvent(DbCommand command, IPersistentRepresentation e, IImmutableSet<string> tags)
        {
            var serializationResult = _serialize(e);
            var serializer = serializationResult.Serializer;
            var hasSerializer = serializer != null;

            string manifest = "";
            if (hasSerializer && serializer is SerializerWithStringManifest)
                manifest = ((SerializerWithStringManifest)serializer).Manifest(e.Payload);
            else if (hasSerializer && serializer.IncludeManifest)
                manifest = QualifiedName(e);
            else
                manifest = string.IsNullOrEmpty(e.Manifest) ? QualifiedName(e) : e.Manifest;

            AddParameter(command, "@PersistenceId", DbType.String, e.PersistenceId);
            AddParameter(command, "@SequenceNr", DbType.Int64, e.SequenceNr);
            AddParameter(command, "@Timestamp", DbType.Int64, e.Timestamp);
            AddParameter(command, "@IsDeleted", DbType.Boolean, false);
            AddParameter(command, "@Manifest", DbType.String, manifest);

            if (hasSerializer)
            {
                AddParameter(command, "@SerializerId", DbType.Int32, serializer.Identifier);
            }
            else
            {
                AddParameter(command, "@SerializerId", DbType.Int32, DBNull.Value);
            }

            command.Parameters.Add(new NpgsqlParameter("@Payload", serializationResult.DbType) { Value = serializationResult.Payload });

What I don't know, can't debug and don't know by heart, the Journal code checks with e.Payload and seems to pretty much ignore serializationResult? @Aaronontheweb or @Arkatufus will know this better :)

For what it's worth, the above Journal code can be refactored to something like this:

        protected override void WriteEvent(
            DbCommand command,
            IPersistentRepresentation e,
            IImmutableSet<string> tags)
        {
            var serializationResult = _serialize(e);
            var serializer = serializationResult.Serializer;

            var manifest = serializer switch
            {
                SerializerWithStringManifest stringManifest => stringManifest.Manifest(e.Payload),
                { IncludeManifest: true } => QualifiedName(e),
                _ => !string.IsNullOrEmpty(e.Manifest) ? e.Manifest : QualifiedName(e),
            };

            AddParameter(command, "@PersistenceId", DbType.String, e.PersistenceId);
            AddParameter(command, "@SequenceNr", DbType.Int64, e.SequenceNr);
            AddParameter(command, "@Timestamp", DbType.Int64, e.Timestamp);
            AddParameter(command, "@IsDeleted", DbType.Boolean, false);
            AddParameter(command, "@Manifest", DbType.String, manifest);
            AddParameter(command, "@SerializerId", DbType.Int32, (object?) serializer?.Identifier ?? DBNull.Value);

            command.Parameters.Add(new NpgsqlParameter("@Payload", serializationResult.DbType) { Value = serializationResult.Payload });

Might be worth it to simplify the hasSerializer stuff in this PR too

[Arkatufus]

That is the peculiarity of PostgreSql extension. If you set the PostgreSql data type to either JSONB or JSON, the internal Akka.NET serializer is completely ignored and the plugin will attempt to serialize the paylod using NewtonSoft.Json completely. And since the the JSON serializer already embeds type information, we do not need manifest anymore.

[Arkatufus]

Yes, we know that this is a very bad design, the PostgreSql extension should not offer to save the data in JSON nor JSONB to begin with.

[CumpsD]

It can be handy to have JSON to be honest. It's a very versatile format without any lock-in. And it makes for easy debugging ;)

[Arkatufus]

Except when a user complained that their production deployment is failing because a serializer kept throwing circular reference exception when they're using Hyperion for everything.