Added new code sections to support deser overrides

[timocov]

Issue #, if available: fixes #1053

Description of changes:

I was playing around with the code in order to find a good solution for #1053 and it seems this is the one (well, at least it works, it doesn't expose too much and kinda fits into current architecture 😂).

To summarize, this PR adds 2 new code sections that consuming code can override:

• MemberDeserializerSection
• MemberSerializerSection

For instance, considering an example from #1053 (comment) you can write something like that in your codegen integration in order to get proper deser and type change:

final class MemberSerializerInterceptor implements CodeInterceptor<MemberSerializerSection, JavaWriter> {
    private final CodeGenerationContext context;

    public MemberSerializerInterceptor(CodeGenerationContext context) {
        this.context = context;
    }

    @Override
    public Class<MemberSerializerSection> sectionType() {
        return MemberSerializerSection.class;
    }

    @Override
    public void write(JavaWriter writer, String previousText, MemberSerializerSection section) {
        section.targetedShape().accept(new Visitor(context, writer, previousText, section));
    }

    private static class Visitor extends ShapeVisitor.Default<Void> {
        private final CodeGenerationContext context;
        private final JavaWriter writer;
        private final String previousText;
        private final MemberSerializerSection section;

        public Visitor(CodeGenerationContext context, JavaWriter writer, String previousText, MemberSerializerSection section) {
            this.context = context;
            this.writer = writer;
            this.previousText = previousText;
            this.section = section;
        }

        @Override
        public Void stringShape(StringShape stringShape) {
            if (stringShape.hasTrait(DateFormatTrait.class)) {
                writer.putContext("state", section.state());
                writer.putContext("schema", section.shapeSchemaVariable());
                writer.write("SharedSerde.serializeDate(${schema:L}, ${state:L}, serializer)");
                return null;
            }

            return getDefault(stringShape);
        }

        @Override
        public Void memberShape(MemberShape memberShape) {
            return context.model().expectShape(memberShape.getTarget()).accept(this);
        }

        @Override
        protected Void getDefault(Shape shape) {
            writer.writeWithNoFormatting(previousText);
            return null;
        }
    }
}

final class MemberDeserializerInterceptor implements CodeInterceptor<MemberDeserializerSection, JavaWriter> {
    private final CodeGenerationContext context;

    public MemberDeserializerInterceptor(CodeGenerationContext context) {
        this.context = context;
    }

    @Override
    public Class<MemberDeserializerSection> sectionType() {
        return MemberDeserializerSection.class;
    }

    @Override
    public void write(JavaWriter writer, String previousText, MemberDeserializerSection section) {
        section.targetedShape().accept(new Visitor(context, writer, previousText, section));
    }

    private static class Visitor extends ShapeVisitor.Default<Void> {
        private final CodeGenerationContext context;
        private final JavaWriter writer;
        private final String previousText;
        private final MemberDeserializerSection section;

        public Visitor(CodeGenerationContext context, JavaWriter writer, String previousText, MemberDeserializerSection section) {
            this.context = context;
            this.writer = writer;
            this.previousText = previousText;
            this.section = section;
        }

        @Override
        public Void stringShape(StringShape stringShape) {
            if (stringShape.hasTrait(DateFormatTrait.class)) {
                writer.putContext("schemaName", section.shapeSchemaVariable());
                writer.putContext("deserializer", section.deserializerVariable());
                writer.write("SharedSerde.deserializeDate(${schemaName:L}, ${deserializer:L})");
                return null;
            }

            return getDefault(stringShape);
        }

        @Override
        public Void memberShape(MemberShape memberShape) {
            return context.model().expectShape(memberShape.getTarget()).accept(this);
        }

        @Override
        protected Void getDefault(Shape shape) {
            writer.writeWithNoFormatting(previousText);
            return null;
        }
    }
}

This doesn't feel like a huge change (even tho it might expose something you don't want to expose - let me know) and the amount of changes is relatively small, but it feels like it gives enough flexibility for consumers if they need to (e.g. I also was able to add support for alloy#discriminated as well, which feels like a huge win tbh 😂)

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