refactor: rename plugin manager to plugin client and rename path from manager to impl (#18876)

api/services/plugin/oauth_service.py

@@ -0,0 +1,7 @@
+from core.plugin.impl.base import BasePluginClient
+
+
+class OAuthService(BasePluginClient):
+    @classmethod
+    def get_authorization_url(cls, tenant_id: str, user_id: str, provider_name: str) -> str:
+        return "1234567890"