Support for sending invitations also to enquiry forms.
Invitation to enquiry should not contain contact address parameter instead an existing entity must be selected (its contact address is used to send a message with invitation). Internally issued invitation should also hold information on whether it is to enquiry or to reg form.
Enquiry form should be enriched by a new flag: by invitation only. Such enquires shouldn't be available in a regular way on the separate endpoint nor presented after login on endpoint nor in sticky enquires list.
When enquiry by invitation is accessed (using invitation link) then it should be loaded on a similar way as current registration forms by invitation are: same endpoint, no authentication and effective user is obtained from invitation.