React Native and User credential validation against CRM HubSpot.

I’m developing a React Native mobile app which requires the user to create an account and login into the app. I’m als using the HubSpot CRM system in which I want to manage all the user accounts. When the user signs into the App the user name and password needs to be validated against the user credentials in the HubSpot CRM. Does anybody have hints and tips on how to do this? Do I have to use OAuthV2? I can use the React fetch methode to check the user credentials but that is probably not the best way forward. Looking for suggestions and examples. Thanks.