Add "Not Interested" state option to workshop inquiry submissions

[maneesha]

If someone submits a workshop inquiry form, we should have the option to mark it as "Not Interested" and consider that submission closed.

The current options of Accept and Discard do not work for this case. When someone makes an inquiry, they are not yet committing to anything so we don't want to accept it until we know they want to do a workshop. We also do not want to discard as we want to keep the record of this inquiry. This should include the option to re-open it if the submitter decides they want to run the workshop after all.

The "Not Interested" state should only apply to workshop inquires, not workshop requests or self organized submissions.

[maneesha]

@elichad @pbanaszkiewicz do you need more information to implement this feature?

[pbanaszkiewicz]

@maneesha no, you can add it to the milestone backlog.