Spec 1 on 1 Chats

[iurimatias]

[osmaczko]

Double Ratchet is well isolated in its own library: https://github.com/status-im/doubleratchet and follows Signal's specifications.

[jrainville]

@osmaczko do you plan on finishing this spec task for 2.35?

[sunleos]

please reopen if it is still valid