Add requires_zed_cla column to channels table

Don't allow granting guests write access in a call where the channel
or one of its ancestors requires the zed CLA, until that guest has
signed the Zed CLA.

Co-authored-by: Marshall <marshall@zed.dev>

crates/collab/src/db/queries/channels.rs

@@ -67,6 +67,7 @@ impl Database {
                         .as_ref()
                         .map_or(String::new(), |parent| parent.path()),
                 ),
+                requires_zed_cla: ActiveValue::NotSet,
             }
             .insert(&*tx)
             .await?;
@@ -261,6 +262,22 @@ impl Database {
         .await
     }
 
+    #[cfg(test)]
+    pub async fn set_channel_requires_zed_cla(
+        &self,
+        channel_id: ChannelId,
+        requires_zed_cla: bool,
+    ) -> Result<()> {
+        self.transaction(move |tx| async move {
+            let channel = self.get_channel_internal(channel_id, &*tx).await?;
+            let mut model = channel.into_active_model();
+            model.requires_zed_cla = ActiveValue::Set(requires_zed_cla);
+            model.update(&*tx).await?;
+            Ok(())
+        })
+        .await
+    }
+
     /// Deletes the channel with the specified ID.
     pub async fn delete_channel(
         &self,