Unable to lookup for metadata controlled by authority in edit view

[PabloDeAlbu]

Describe the bug When someone try to add a metadata controlled by authority from /items/[uuid]/edit/metadata, it's not possible to add the authority key. In DSpace 6 it is possible to do this through a "Lookup" button, as you can see in the following image taken from the demo

in dspace 7 you can only add a metadata, but not its authority key

the way I have found to add the authority key is through the metadata-import feature, by specifying the authority key in a csv file

To Reproduce Steps to reproduce the behavior:

1. Configure a metadata to be controlled by authority, for example dc.​contributor.​author
2. try to add a metadata with an authority key from /items/[uuid]/edit/metadata

Expected behavior There should be some lookup button like in dspace 6