ASP.NET Public API for Transactions

I need an ASP.NET Web API that external partners can safely call to create, read, update, and delete transactional data. The service will sit in front of an existing external database, so the project covers building the endpoints and wiring them to that data source through Entity Framework (or another lightweight ORM if you can justify the choice). I’m interested in a clean REST-style design, proper HTTP status use, and solid exception handling so third-party developers can integrate without surprises.

Key deliverables:
• Fully functional ASP.NET Web API project targeting .NET 6 or later
• CRUD endpoints for all transactional entities mapped to the external database
• Token-based authentication and role-based authorization
• Swagger / OpenAPI docs generated from the code comments
• A concise README explaining build, run, and environment variables

I’ll provide connection details for the external database and a sample dataset once we start. Please structure the solution so I can extend it with additional entities later, keep the controller logic thin, and follow standard dependency-injection patterns for maintainability.