Outfactor shared logic in input components

Okay, considering the `exportResult` function from `spindle.component.ts`:

```typescript
public parse(): void {
this.form.controls.mpInput.markAsTouched();
this.form.controls.mpInput.updateValueAndValidity();
const input = this.form.controls.mpInput.value;
if (this.form.invalid || !input) {
return;
}
this.apiService.input$.next(input);
}
```

These functions are very similar: could we think of a good way to make them generalizable / put them in a service? Is that even worthwhile, do you think? I'm happy to let this rest since it's not really priority but I was wondering all the same.

_Originally posted by @Meesch in https://github.com/CentreForDigitalHumanities/parseport/pull/84#discussion_r1907241970_

Start by reading the exportResult function in spindle.component.ts alongside the parse function shown in the issue, then locate the other similar input-component functions. Determine whether their shared logic can be generalized without obscuring component-specific behavior; done means an agreed reusable design and corresponding refactor, with tests updated if existing coverage applies.

Written by the indexing model from the issue text.