Add Gunicorn settings to correctly receive header

[raftmsohani]

Description:
Gunicorn is python package that serves Django application as WSGI HTTP server. The existing configuration for Gunicorn is from the cmd line:
gunicorn tdpservice.wsgi:application --bind 0.0.0.0:8080 --timeout 10 --workers 3 --log-file=- --log-level $LOGGING_LEVEL
Due to security compliance issues with RFC3875 Gunicorn shows REMOTE_ADDR as IP address and additionally drops any header that is coming from an untrusted proxy. We have to add Nginx as a trusted source for forwarded headers and additionally change setting to receive all headers securely (should we decide to use them in the logic).
This issue is ultimately related to Nginx (issue #1544 ) settings to have the headers being forwarded to Gunicorn.

Acceptance Criteria:

• Django receives client http headers
• Django receives custom http headers
• Testing Checklist has been run and all tests pass
• README is updated, if necessary

Tasks:

• add --forwarded-allow-ips="*" to Gunicorn start cmd
• Run Testing Checklist and confirm all tests pass

Notes:

• During deployment, Nginx's IP address should replace '*' to add more security

Supporting Documentation:
Please include any relevant log snippets/files/screen shots

• Gunicorn deployment with Nginx
• Gunicorn documentation
• How to Build a Django and Gunicorn Application with Docker

Open Questions:

• Should we use socket? (to ncrease performance)