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/04_auth.up.sql

@@ -0,0 +1,39 @@
+begin;
+
+  -- base table for auth methods
+  create table auth_method (
+    auth_method_id wt_public_id primary key
+  );
+
+
+  -- base table for auth accounts
+  create table auth_account (
+    auth_account_id wt_public_id primary key
+  );
+
+
+  create or replace function
+    insert_auth_method_subtype()
+    returns trigger
+  as $$
+  begin
+    insert into auth_method (auth_method_id)
+    values
+      (new.auth_method_id);
+    return new;
+  end;
+  $$ language plpgsql;
+
+  create or replace function
+    insert_auth_account_subtype()
+    returns trigger
+  as $$
+  begin
+    insert into auth_account (auth_account_id)
+    values
+      (new.auth_account_id);
+    return new;
+  end;
+  $$ language plpgsql;
+
+commit;