Azure Secure API integration With OAuth 2.0 And per user

"Hi Everyone, I hope you are doing well in your career. Actually, I am very new to the Azure and D365 world and facing a problem with a small requirement. If any of you can help me out, I would be really grateful.

Problem Statement:
I want to integrate an External System with D365. The external system uses OAuth 2.0 Authentication, and we need integration based on a per-user concept. This means we need to use Azure for storing the API credentials, and a C# plugin (not sure) for API calls (API credentials are not exposed directly in C# Code)."