Container issue: Make HTTP requests using IHttpClientFactory

This is the Container issue for this doc. Reopen each issue you are working on so the owner is notified.

PU issues:

- [ ] How to create named clients at runtime / after Startup #16638
- [x] Not clear that AddHttpClient replaces AddScoped, AddTransient, etc #16498
- [x] HTTP POST example? #12580
- [ ] Disposing of Dependencies Injected into Custom DelegatingHandlers #18058
- [ ] Disposing HttpResponseMessage #16103
- [ ] Configuring ALL HttpClients named or unnamed #18162
- [ ]
- [ ]
- [ ]
Not PU:


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#### Document Details

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* ID: 881cef77-11ef-ac11-06d0-0996a1ccfa1b
* Version Independent ID: 3d356334-e672-7e8b-1fef-7944ebee99eb
* Content: [Make HTTP requests using IHttpClientFactory in ASP.NET Core](https://docs.microsoft.com/en-us/aspnet/core/fundamentals/http-requests?view=aspnetcore-2.2#feedback)
* Content Source: [aspnetcore/fundamentals/http-requests.md](https://github.com/aspnet/AspNetCore.Docs/blob/master/aspnetcore/fundamentals/http-requests.md)
* Product: **aspnet-core**
* Technology: **aspnetcore-fundamentals**
* GitHub Login: @stevejgordon
* Microsoft Alias: **scaddie**