[services] derive serialize/deserialize for WorkflowInProgress enum

Summary:
we need to serialize/deserialize this enum so we can store it in and then retrieve and deserialize it from DynamoDB

Depends on D11150

Test Plan:

• call login start RPC, log the serialized and deserialized values
• successfully log in
• call register start RPC, log the serialized and deserialized values
• successfully register
• call update password start RPC, log the serialized and deserialized values
• successfully change password

Reviewers: will, michal, bartek

Reviewed By: michal

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D11160