[native] enum for grpc client data

Summary:
We will pass this enum as a param to the login helper functions to distinguish between the registration and login workflows.

Depends on D4876

Test Plan: cargo build (dead code)

Reviewers: tomek, karol, atul

Reviewed By: tomek

Subscribers: ashoat, abosh

Differential Revision: https://phab.comm.dev/D4878