Add custom nuget source

**Describe the bug**

We have our own github nuget package source we add for building our project. We're using the new static web app CI/CD feature which integrates automatically with your github repo. We are unable to add our own nuget source using this task.
The app (UI) is written using the React framework. The api (backend functions) is written using .NET Core 3.1
[static_web_app.txt](https://github.com/Azure/static-web-apps/files/6710607/static_web_app.txt) - github workflow file

**To Reproduce**
Steps to reproduce the behavior:
1. Set up the static web app CI/CD flow (according to documentation)
2. Add an app to be built & deployed
3. Add an api to be built & deployed
4. Add steps to add custom nuget source (for which you need a token to authorize access to)
5. Trigger build
6. Check logs (see screenshots below)

**Expected behavior**
How can we add a custom nuget source as part of this workflow?
Or is there another preferred way to go about this?
The idea is to have the functions (which act as a gateway) & the react app to be deployed together.

**Screenshots**

**Additional context**
Also tried adding the nuget source using a separate step followed by the task to build the static web app. But it also did not work:

Any feedback is welcome at this point. For now we just deploy the functions using a separate repo and workflow.
The react app is, for now, the only one being deployed in the static web app resource.