Allow for more than one item type in the Submission Form

[alawvt]

Is your feature request related to a problem? Please describe. In DSpace 6 XMLUI, the submitter can select more than one item type. This is helpful for compound items, for example a presentation with a combination of video, slides, poster, and proceedings files. A shortcoming of the implementation is that only one of item type customizatons appears on page two of the submission form.

In DSpace 7, the submitter may only select one item type in the submission form.

In both versions, the metadata model, itself, supports multiple items types.

Describe the solution you'd like The ideal would be to support multiple items types and to also provide the form elements for all of the item types, as described in https://wiki.lyrasis.org/display/DSDOC7x/Submission+User+Interface#SubmissionUserInterface-ItemtypeBasedMetadataCollection.

This is not as high a priority for us as other issues, but we do want to document this current functionality.

Describe alternatives or workarounds you've considered A clear and concise description of any alternative solutions or features you've considered.

Additional context Add any other context or screenshots about the feature request here.