Add CredentialService to handle user credentials

src/backend/langflow/services/credentials/service.py

@@ -0,0 +1,29 @@
+from typing import TYPE_CHECKING, Union
+from uuid import UUID
+
+from fastapi import Depends
+from sqlmodel import Session
+
+from langflow.services.auth import utils as auth_utils
+from langflow.services.base import Service
+from langflow.services.database.models.credential.model import Credential
+from langflow.services.deps import get_session
+
+if TYPE_CHECKING:
+    from langflow.services.settings.service import SettingsService
+
+
+class CredentialService(Service):
+    name = "credential_service"
+
+    def __init__(self, settings_service: "SettingsService"):
+        self.settings_service = settings_service
+
+    def get_credential(self, user_id: Union[UUID, str], name: str, session: Session = Depends(get_session)) -> str:
+        # we get the credential from the database
+        credential = session.query(Credential).filter(Credential.user_id == user_id, Credential.name == name).first()
+        # we decrypt the value
+        if not credential:
+            raise ValueError(f"{name} credential not found.")
+        decrypted = auth_utils.decrypt_api_key(credential.value, settings_service=self.settings_service)
+        return decrypted