[Feat] Use server workers (Gunicorn)

[erwanschild]

Is your feature request related to a problem? Please describe.

Use Gunicorn to run the application an several processes and to be able to handle more requests (scalability & replication)

Describe the solution you'd like

• dependencies: add gunicorn,
• run the app: use gunicorn main:app --workers 4 --worker-class or uvicorn main:app --host 0.0.0.0 --port 8080 --workers 4.

Additional context

See https://fastapi.tiangolo.com/deployment/server-workers/