feat: make dropping users_email_key backward compatible (#995)

Dropping the `users_email_key` can sometimes be an issue as the
`auth.users.email` column has been used as a foreign key reference in
certain projects. This PR will continue with the migration, but will
raise a notice that the developers of such projects should take care of
this change manually. If it is not handled, SSO will not work and future
compatibility with new versions may be an issue.

Author: hf

migrations/20221215195500_modify_users_email_unique_index.up.sql

@@ -8,9 +8,16 @@ alter table only {{ index .Options "Namespace" }}.users
 
 comment on column {{ index .Options "Namespace" }}.users.is_sso_user is 'Auth: Set this column to true when the account comes from SSO. These accounts can have duplicate emails.';
 
+do $$
+begin
+  alter table only {{ index .Options "Namespace" }}.users
+    drop constraint if exists users_email_key;
+exception
+-- dependent object: https://www.postgresql.org/docs/current/errcodes-appendix.html
+when SQLSTATE '2BP01' then
+  raise notice 'Unable to drop users_email_key constraint due to dependent objects, please resolve this manually or SSO may not work';
+end $$;
+
 create unique index if not exists users_email_partial_key on {{ index .Options "Namespace" }}.users (email) where (is_sso_user = false);
 
 comment on index {{ index .Options "Namespace" }}.users_email_partial_key is 'Auth: A partial unique index that applies only when is_sso_user is false';
-
-alter table only {{ index .Options "Namespace" }}.users
-  drop constraint if exists users_email_key;