[Documentation] Elaborate on Background Service calling Web API

[FIMTooler]

Documentation related to component

Microsoft.Identity.Web

Please check all that apply

• typo
• documentation doesn't exist
• documentation needs clarification
• error(s) in the example
• needs an example

Description of the issue

Took me a while to find this example of Background Service calling Web API, but glad that I did! The Program.cs example is very clear and easy to follow, however the Worker.cs only demonstrates 1 of the 3 options presented in the Program.cs - the downStreamAPI.

Could you please clarify what object should be injected into the Worker class if you're not using either downStreamAPI or GraphServiceClient?

tests/DevApps/ContosoWorker/Worker.cs