Add gateway name to the HTTP integration's JSON payload

[cdrx]

• [x] The issue is present in the latest release.
• [x] I have searched the issues of this repository and believe that this is not a duplicate.

What happened?

I am using the HTTP integration with the legacy payload format. I'm trying to add support for the newer format, but it is missing the gateway's name key from the rxInfo object.

What did you expect?

This field is present in the legacy payload, but not the newer JSON payload.

Can it be added? I'm happy to implement and open a PR if you could give me a steer on where to look.

Steps to reproduce this issue

Steps:

1. Enable the HTTP integration on an application, using the legacy payload
2. Inspect the output
3. Change the format to non-legacy payload
4. Inspect the output, name is missing

Your Environment

All deployed via Docker, running versions:

chirpstack/chirpstack-network-server:3.15.3                        
chirpstack/chirpstack-application-server:3.17.3
chirpstack/chirpstack-gateway-bridge:3.13.1    
chirpstack/chirpstack-gateway-bridge:3.13.1    
chirpstack/chirpstack-gateway-bridge:3.13.1    
postgres:11.13-alpine                          
redis:6.2.6