auth method schema (#131)

* Rename iam migrations to 06

* Add base tables for auth methods and auth accounts

* Add triggers for auth_method and auth_account subtypes

internal/db/migrations/postgres/06_iam.down.sql

@@ -0,0 +1,16 @@
+BEGIN;
+
+drop table iam_group cascade;
+drop table iam_user cascade;
+drop table iam_scope_project cascade;
+drop table iam_scope_organization cascade;
+drop table iam_scope cascade;
+drop table iam_scope_type_enm cascade;
+drop table iam_role cascade;
+
+
+drop function iam_sub_names cascade;
+drop function iam_immutable_scope_type_func cascade;
+drop function iam_sub_scopes_func cascade;
+
+COMMIT;