Unlikely because you aren't going to share personal, identifiable information with this service; you would just send the primary key of the user in your database (usually an integer, guid, etc, as long as you aren't using some string that includes personal information like email or possibly username where they user picks their own name).
You can share all the information you want with other entities under GDPR as long as the information you are sending as long as you can't uniquely identify someone from that data _without_ additional information.
You can share all the information you want with other entities under GDPR as long as the information you are sending as long as you can't uniquely identify someone from that data _without_ additional information.