feat(auth): add assignable user permissions

internal/database/testdata/migrations/001_create_users.up.sql

@@ -1,5 +1,7 @@
 CREATE TABLE users (
     id         BIGSERIAL PRIMARY KEY,
     username   TEXT NOT NULL UNIQUE,
+    role       TEXT,
+    permissions TEXT[] DEFAULT '{}'::TEXT[] NOT NULL,
     created_at TIMESTAMPTZ NOT NULL DEFAULT now()
 );