channel projects (#8456)

Add plumbing for hosted projects. This will currently show them if they
exist
but provides no UX to create/rename/delete them.

Also changed the `ChannelId` type to not auto-cast to u64; this avoids
type
confusion if you have multiple id types.


Release Notes:

- N/A

crates/notifications/src/notification_store.rs

@@ -1,6 +1,6 @@
 use anyhow::{Context, Result};
 use channel::{ChannelMessage, ChannelMessageId, ChannelStore};
-use client::{Client, UserStore};
+use client::{ChannelId, Client, UserStore};
 use collections::HashMap;
 use db::smol::stream::StreamExt;
 use gpui::{
@@ -413,7 +413,7 @@ impl NotificationStore {
             Notification::ChannelInvitation { channel_id, .. } => {
                 self.channel_store
                     .update(cx, |store, cx| {
-                        store.respond_to_channel_invite(channel_id, response, cx)
+                        store.respond_to_channel_invite(ChannelId(channel_id), response, cx)
                     })
                     .detach();
             }