Fix validation rule bug for registration

[michalsn]

When we try to register a user using PostgreSQL, we receive an error:

pg_query(): Query failed: ERROR: invalid input syntax for integer: "{id}" LINE 4: AND "id" != '{id}'

This wasn't popping up when using MySQL, because PostgreSQL is more restrictive. So, running the query:

SELECT 1 FROM "users" WHERE "email" = '[email protected]' AND "id" != '{id}' LIMIT 1

is fine on mysql but not really on postgresql. But in both cases, it's a bug actually.

The fix comes down to changing the validation rules for registration.