User Authentication for App

I have a website with Gravity Forms where logged-in users can submit data. I want to create a mobile app using REST API where users can log-in and submit gravity forms using REST API. What is the best way to enable all the users on the website to log-in through the mobile app and submit gravity form via REST API?

I was able to submit sample data via REST API but had to create an “Application Password” for the user. How do I enable this for every user of the website without them having to generate a new application password?