- Prior to this change using asp-page-handler on its own did not create correct `<form>` elements. There were multiple issues, one as that the `FormTagHelper` would purposefully drop into a no-op code path. Second is the `DefaultHtmlGenerator` didn't call through to the `UrlHelper` correctly.
- Added functional test cases to validate asp-page-handler can live on its own on a form tag. This also included adding a variant where method="post".
- Added a `FormTagHelper` unit test to validate the `PageHandler` property is consumed properly.
#6208
