Remove Bitstreams on edit-item-page doesn't work

[Leano1998]

Describe the bug
A new issue appeared, where you can't remove the bitstreams of an item using the edit-item-page. After selecting bitstreams for deletion, the Save-button stays deactivated. Only if you select bitstreams of all existing bundles, the button is clickable.

To Reproduce
Steps to reproduce the behavior:

1. Login as an site-administrator
2. Open the edit-item-page of an item with attached bitstreams
3. Navigate to the Bitstreams-tab.
4. Click on the tiny garbage-can of one bitstream for deleting it.
5. Try to click Save in order to apply the changes (you can also try to Discard the changes, it won't work either)

Expected behavior

The Save or Discard buttons should be clickable.

[tdonohue]

This is reproducible on Sandbox and Demo. Not sure why/how this is occurring or when it began.

@artlowel or @atarix83 : Do either of your teams have time to look into this quickly early next week?

[Leano1998]

So, I looked a bit into this and it seems to be a problem, that the hasChanges() is not longer called directly in the async pipe, but via the variable hasChanges$ in the item-bitstreams.component.html:

    <button class="btn btn-primary" [disabled]="(hasChanges$ | async) !== true || submitting"
            [attr.aria-label]="'item.edit.bitstreams.save-button' | translate"
            (click)="submit()">

If I change it back in calling hasChanges() directly it works. It has been changed during another bugfix in here: #3060

@alexandrevryghem: Do you remember, why you changed this?

[alexandrevryghem]

@Leano1998 : It's because it causes performance issues, I can take a look at this

[Leano1998]

Ah, I thought so, Thank you @alexandrevryghem

[tdonohue]

Thanks @alexandrevryghem ! I'll assign this to you then.