No way to use DeserializeSeed when deserializing from Reader

[gmilleramilar]

As far as I can tell, The only Deserializer made public through the API is one that reads from a pre-parse BSON value:

https://docs.rs/bson/2.14.0/bson/struct.Deserializer.html

I have a use case where I'm doing a custom decoding (from bytes), and would like to use a serde::de::DeserializeSeed. However this is impossible, because the raw Deserializer is hidden behind methods like from_reader().

Could a raw (bytes) Deserializer be made public?