Form Controller

FormController is the engine object behind every mounted MLForm.

Member	Purpose
`fields`	Ordered field controllers.
`reports`	Ordered report controllers.
`state`	Current form state snapshot.
`getField(id)`	Find one field.
`getReport(id)`	Find one report.
`getValues()`	Read current runtime values.
`setValues(values)`	Patch field values.
`validate()`	Run field and form validators.
`submit(options?)`	Validate, submit through transport, resolve reports.
`abortSubmit(reason?)`	Abort pending submit.
`reset()`	Restore initial values and idle state.
`subscribe(listener)`	Listen to complete form state.
`subscribeSelector(selector, listener, options?)`	Listen to a derived value.

const unsubscribe = mounted.form.subscribeSelector(
  (state) => state.status,
  (status) => console.log(status),
  { emitInitial: true },
);

unsubscribe();

submit() throws ValidationError, SubmitError, or SubmissionAbortedError when the operation cannot complete.