[keyserver] Copy/paste createAccount to createSIWEAccount
Summary:
NOTE: This diff is solely to make the next diff easier to review.
If I just introduce createSIWEAccount with the changes already made it's a lot harder to make sense of the differences.
Test Plan: NA, this diff is just to make the next diff easier to review.
Reviewers: ashoat, tomek
Reviewed By: ashoat
Differential Revision: https://phab.comm.dev/D6076