[sql] added ethereum_address to users table

Summary:
self explanatory
linear task

Test Plan:
run keyserver & watch it migrate.
also run

mysql -u root -p
...
DROP DATABASE comm;
CREATE DATABASE comm;

Reviewers: varun, atul, ginsu, tomek, ashoat

Reviewed By: tomek, ashoat

Subscribers: tomek, abosh, varun, ginsu, atul, ashoat

Differential Revision: https://phab.comm.dev/D5566