Add fields for mobile network connectivity attributes

[bryce-b]

• The following fields need to be added:
  net.host.connection_type: 5G,4G,3G,2G,1G, wifi,unavailable (String)
  net.host.carrier.mcc : mobile country codes (String)
  net.host.carrier.mnc : mobile network codes (String)
  net.host.carrier.name: Carrier names (String) (e.g.: T-Mobile, AT&T, etc)
  net.host.carrier.icc: 2-character iso country code (String) (e.g.: US, DE)

• These fields also need to be added into ECS

Note: Here are related tickets
OpenTelemetry spec issue
iOS agent ticket

[bryce-b]

Here's a link to a rudimentary test app for generating iOS data: https://github.com/elastic/ios-integration-testing
It requires MacOS.
the apm server ip/url can be set in this file : https://github.com/elastic/ios-integration-testing/blob/master/Shared/Model/ios_integration_testingApp.swift
Let me know if you need help getting it set up.

[axw]

We should keep #4912 in mind when we do this - specifically there's overlap on net.host.connection_type.

[jalvz]

@bryce-b should any of these fields be required?

[bryce-b]

@jalvz what are the implications of being 'required'? Will the traces be ignored if they are not attached? If so, they shouldn't be required.

[jalvz]

Exactly, thanks 👍