Adjust which spaces are added to add to space list

[ggurdin]

After selected a bunch of chats and going to "add to space," you get a list with all the spaces and all the chats can be added to. That change we want to make is to have that list instead be spaces that any of the chats can be added to. After clicking on the space name, the user should see a popup saying something like "only x and y chat can be added to this space", so they know what's going on.

@Kelrap talk to Gabby or Will before starting this for a clearer explanation