Expose SerialModule in KMongoSerializationRepository

[bizarre]

We're using kmongo alongside ktor and using Kotlinx Serialization on both sides. We'd like to be able to use the same models that we use for kmongo with ktor, but none of the bindings are exposed publicly. We're currently using a less than ideal reflection solution to fetch the module getter in KMongoSerializationRepository and then passing that directly into the constructor of kotlinx.serialization.json.Json.

[zigzago]

@bizarre a PR would be appreciated. KMongo allows to add modules using org.litote.kmongo.serialization.registerModule function. Not sure to understand well why you need to access to KMongoSerializationRepository.module ;)

[bizarre]

@zigzago For example, let's say we have a Id<Model> field in an object. Kmongo has no problem serializing it because the serializer (IdSerializer, I believe) is available in its SerialModule. However, if we want to serialize the same object in an external serial format, kotlinx.serialization won't be able to find the serializer since its not in context. If KMongoSerializationRepository.module is exposed then we'd be able to add all the kmongo-specific serializers into context.

[zigzago]

Merged