Feature: #110873 - Upload files by pasting them from the clipboard 

Description 

Files can now be uploaded to the folder shown in the Media module by pasting them from the clipboard, in addition to dragging them onto the module or choosing them with the upload button.

This covers files copied in the file manager of the operating system as well as image data, such as a screenshot taken to the clipboard. A pasted file runs through the same upload as a dropped one, including the dialog asking what to do with a file that already exists in the folder.

Pasting into a form field of the module, such as the search field, keeps its usual behaviour and does not upload anything.

Files can also be pasted into a file field of a record, such as the Images field of a content element, both in the editing form and in the contextual record edit. The files are uploaded to the file field the editor clicked into or focused last. Without such an interaction, they are uploaded to the file field if only one is visible. If several file fields are visible, the editor selects the field to add the files to in a modal. The allowed file extensions of the field apply, and the uploaded files are added to the field.

While files are dragged over a record, each of its file fields is covered by its dropzone, as in the Media module, so the files can be dropped anywhere onto the field instead of onto a small bar below it.

The file browser, opened for example with Add image in a file field, now uses the same upload. Files can be uploaded to the folder shown by choosing them with the upload button, by dropping them anywhere onto the content area of the file browser and by pasting them. Afterwards the folder is reloaded, so the uploaded files can be selected right away. The allowed file extensions of the field apply. The Overwrite existing files toggle of the previous upload form is replaced by the dialog asking what to do with a file that already exists.

Impact 

Files can be uploaded in the Media module and in the file browser, and added to file fields of records, with Cmd+V or Ctrl+V without dragging them from another window.