hosted projects (#8627)

- **Allow joining a hosted project**

You can't yet do anything in a hosted project, but you can join it and
look how empty it is.

Release Notes:

- N/A

crates/client/src/user.rs

@@ -24,6 +24,9 @@ impl std::fmt::Display for ChannelId {
     }
 }
 
+#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Copy)]
+pub struct HostedProjectId(pub u64);
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub struct ParticipantIndex(pub u32);