Investigate Optimizing JsonFlatten Serialization

[alzimmermsft]

Investigate manually handling JsonFlatten serialization instead of writing the object to a tree and mutating nodes. The following is code which was an initial investigation along with comments of its short-comings:

// Investigation into serializing the class ourselves to prevent string manipulation.
// Code below doesn't handle the following:
// - Null values are serialized without respecting ObjectMapper inclusion.
// - JsonType information isn't included.
if (defaultSerializer instanceof BeanSerializer) {
    BeanSerializer beanSerializer = (BeanSerializer) defaultSerializer;

    jgen.writeStartObject();

    Iterator<PropertyWriter> writerIterator = beanSerializer.properties();
    while (writerIterator.hasNext()) {
        BeanPropertyWriter writer = (BeanPropertyWriter) writerIterator.next();
        String jsonPropertyName = writer.getName();
        if ((writer.getMember().hasAnnotation(JsonFlatten.class) || classHasJsonFlatten)
            && CHECK_IF_FLATTEN_PROPERTY_PATTERN.matcher(jsonPropertyName).matches()) {
            String[] flatteningNames = SPLIT_FLATTEN_PROPERTY_PATTERN.split(jsonPropertyName);

            jgen.writeFieldName(flatteningNames[0]);
            jgen.writeStartObject();

            for (int i = 1; i < flatteningNames.length - 1; i++) {
                jgen.writeFieldName(flatteningNames[i]);
                jgen.writeStartObject();
            }

            jgen.writeFieldName(flatteningNames[flatteningNames.length - 1]);
            writeValue(jgen, writer, value);

            for (int i = 1; i < flatteningNames.length - 1; i++) {
                jgen.writeEndObject();
            }

            jgen.writeEndObject();
        } else {
            jgen.writeFieldName(jsonPropertyName);
            writeValue(jgen, writer, value);
        }
    }

    jgen.writeEndObject();

    return;
}

private void writeValue(JsonGenerator jgen, BeanPropertyWriter writer, Object value) {
    try {
        mapper.writeValue(jgen, writer.get(value));
    } catch (Exception e) {
        throw logger.logExceptionAsError(new UncheckedIOException(new JsonGenerationException(e, jgen)));
    }
}

[alzimmermsft]

Closing as this won't be done as the current direction is moving away from usage of this code path