* Add an UnsupportedContentType to the ModelState dictionary when no formatter can read the body.
* Add a filter to the pipeline that searches for that specific exception and transforms the response into 415.
- have one test muted at the moment in our CI
- add `Reset()` action to the service, enabling `// Arrange` to bring `Index()` content to a known state
- add a couple more tests to `TagHelperSampleTest` covering the new action and empty `Index()` list
nits:
- use `ViewData`, not `ViewBag`
jacalvar
Doug Bunting
Pavel Krymets
N. Taylor Mullen