1.2.0

Requires Dart 3.4

• Bumped http to 1.5.0.
• Support request cancellation via Abortable from http.

  You are not required to add abortTrigger to wrapping FetchRequest since it will inherit it by default.
  You can also just use http's AbortableRequest directly if you don't need to customize fetch behavior on a request basis.

• RequestCanceledException how implements RequestAbortedException.
• FetchRequest how also implements Abortable.