Merge remote-tracking branch 'origin/feat/oauth2-migration-20' into feat/oauth2-user-service

merge: интеграция полей OAuth2 миграции в user service.

src/main/resources/db/migration/V2__add_oauth2_fields.sql

@@ -0,0 +1,9 @@
+ALTER TABLE public.users ADD COLUMN provider VARCHAR(20);
+ALTER TABLE public.users ADD COLUMN provider_id VARCHAR(255);
+ALTER TABLE public.users ADD COLUMN created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP NOT NULL;
+
+CREATE UNIQUE INDEX idx_users_provider_provider_id
+    ON public.users(provider, provider_id);
+
+CREATE INDEX idx_users_email ON public.users(email);
+