Allow firebase performance monitoring to track HTTP Requests

[danielgomezrico]

The idea is that all requests done by the library could be tracked using:

• https://firebase.google.com/docs/perf-mon
• android docs: https://firebase.google.com/docs/perf-mon/network-traces?platform=android

We do use that, and it tracks all requests but not those made by this library, Im not sure why.

Your Environment

TODO

• Plugin version:
• Platform: iOS or Android
• OS version:
• Device manufacturer / model:
• Flutter info (flutter doctor):
• Plugin config:

      url: "myendpoint.com",
      locationTemplate: _requestBody(),
      httpRootProperty: '.',
      headers: {
        'Content-Type': 'application/json',
        'Authorization': 'Bearer $authToken'
      },
      params: {
        'device_type': device,
        'reference': loadId,
        'reference_type': 'id',
        'source': 'traxporta',
      },

Expected Behavior

Installing firebase performance monitor should track requests done by this library

Actual Behavior

They are not

Steps to Reproduce

1. Install firebase performance monitor
2. Start the SDK to do HTTP requests to any server
3. The traces do not appear on firebase performance monitor dashboards

Context

We need to monitor the behavior of the requests done from the app, the requests sometimes are not arriving, and we need to understand why.

This library distinct and creates dashboards for requests by:

• status code
• date
• payload size
• timeouts
• custom fields