Implement deleting attachment of message

[Silver-IT]

Problem

There are two features for the attachments in the message. One is Download and the other is Delete. Download feature is done, but Delete feature is not yet.

Solution

Create a gi.contracts/chatroom/deleteAttachment function and implement it.

[taoeffect]

I think for this issue, in addition to implementing support in Vue and the contracts, we need to implement a backend API to support file deletion. So this will have to wait on the proposal that @corrideat is working on to be implemented, because the server needs to do the following:

• It needs to have an API, e.g. /fileDelete
• It needs to be able to verify that the person who is calling this API has permission to delete the file
  • This is easier said than done. For example, we probably want to allow different parties to be able to delete a file. E.g. the group admin should be able to delete the file, and so should the server admin, and of course the person that uploaded it, but nobody else.
• Finally, we need to support updating the accounting for how much is being charge for storage so that the file is no longer being charged for