feat(settings): add SMTP admin configuration

backend/hermes/app/repositories/system_settings_repository.py

@@ -0,0 +1,35 @@
+from collections.abc import Iterable
+
+from sqlalchemy import select
+from sqlalchemy.orm import Session
+
+from app.models.system_setting import SystemSetting
+
+
+class SystemSettingsRepository:
+    @staticmethod
+    def get(db: Session, key: str) -> SystemSetting | None:
+        return db.scalar(select(SystemSetting).where(SystemSetting.key == key))
+
+    @staticmethod
+    def get_many(db: Session, keys: Iterable[str]) -> dict[str, SystemSetting]:
+        key_list = list(keys)
+        if not key_list:
+            return {}
+
+        settings = db.scalars(select(SystemSetting).where(SystemSetting.key.in_(key_list))).all()
+        return {setting.key: setting for setting in settings}
+
+    @staticmethod
+    def upsert(db: Session, *, key: str, value: str, is_secret: bool = False) -> SystemSetting:
+        setting = SystemSettingsRepository.get(db, key)
+        if setting is None:
+            setting = SystemSetting(key=key, value=value, is_secret=is_secret)
+            db.add(setting)
+            db.flush()
+            return setting
+
+        setting.value = value
+        setting.is_secret = is_secret
+        db.flush()
+        return setting