initial mysql support

migrations/mysql/2018-07-11-181453_create_u2f_twofactor/up.sql

@@ -0,0 +1,15 @@
+CREATE TABLE twofactor (
+  uuid      VARCHAR(40) NOT NULL PRIMARY KEY,
+  user_uuid VARCHAR(40) NOT NULL REFERENCES users (uuid),
+  type      INTEGER  NOT NULL,
+  enabled   BOOLEAN  NOT NULL,
+  data      TEXT     NOT NULL,
+
+  UNIQUE (user_uuid, type)
+);
+
+
+INSERT INTO twofactor (uuid, user_uuid, type, enabled, data) 
+SELECT UUID(), uuid, 0, 1, u.totp_secret FROM users u where u.totp_secret IS NOT NULL;
+
+UPDATE users SET totp_secret = NULL; -- Instead of recreating the table, just leave the columns empty