Populate addresses drop-downs with default shipping and return addresses if not already present

Let's assume that both users A and B are participants in an investigation called ID0.

• User A creates an address and selects it as the default shipping address for ID0.
• User B goes to edit the shipping configuration of ID0 ➡ the drop-down menu for the default shipping address is blank because User B does not have access to the address created by User A.

This MR resolves this situation by populating the drop-down menus with the addresses from the shipment, if and only if the user does not have access to these addresses (to avoid duplicates).

This morning's events also changed my mind in regard to disabling the drop-downs when they contain no addresses. Turns out I found it quite frustrating not being able to open the drop-downs even though I knew they were empty...