Can't insert different identifiers in the submission form

[alemarte]

Describe the bug
Inserting different identifiers in a submission doesn't work. The Patch operation is malformed and the submission can't be saved without a full reload of the page.

To Reproduce

1. Login as admin
2. Start a submission in collection Books
3. Insert an identifier of type ISSN and click +
4. Insert an identifier of type Other and click +
5. Save
   

The patch operation

In addition, the submission form results compromised and can be saved again only by refreshing the page.

Expected behavior
I would expect no errors and both values saved.

[alemarte]

Related to this user flow we can find another strange behaviour following this steps:

1. Login as admin
2. Start a submission in collection Books
3. Insert an identifier of type ISSN and click +
4. Save
5. Insert an identifier of type Other and click +
6. Delete the Other record
7. Save

As we can see there is also a remove operation of the wrong metadata containing a /-1 index which is not even compliant with the json patch RFC.

[tdonohue]

I've tentatively pulled this into the Beta 5 board (along with related issues #948 and #949) just for discussion purposes. Once discussed, we may still decide whether to include in Beta 5 or not.

[tdonohue]

As discussed in today's meeting, we expect this bug will be fixed by the (in progress) fix for #971. Therefore, I'm adding a 0hr estimate to this bug. If we later find it is not fixed, then we can reanalyze at that time.