Deck 1.3.0: File-attachments not deletable via API

Update

It's just missing in the docs that an additional optional query param called type must be passed in order to delete file attachments. type can have deck_file (default) or file as value. The latter is required for file attachments which are available since Deck 1.3.0

Original issue

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Describe the bug
The Android Deck App has issues deleting attachments of type file. We call the good old documented delete path, but the API refuses to do anything.

According to the documentation, we call the API as follows:

 @DELETE("v1.0/boards/{boardId}/stacks/{stackId}/cards/{cardId}/attachments/{attachmentId}")
    Observable<Void> deleteAttachment(@Path("boardId") long boardId, @Path("stackId") long stackId, @Path("cardId") long cardId, @Path("attachmentId") long attachmentId);

To Reproduce
Steps to reproduce the behavior:

1. In Android Deck app, open a card with file-type attachment(s)
2. Go to the attachments tab
3. long-press on a file-type attachment
4. select delete
5. see that it doesn't work

Expected behavior
Attachment should be deleted.

Nextcloud version: 21

Deck version: 1.3.0

CC: @stefan-niedermann

Open the linked API documentation for deleting attachments and compare it with the issue's described DELETE path. Document the optional type query parameter, including the deck_file and file values and when file is required. Done means the documentation explains how to delete file-type attachments.