Permissions: Resolve guild, allows ability to delete channels, delete others messages, etc.

src/routes/channels/join_call.rs

@@ -17,6 +17,12 @@ pub async fn req(user: User, target: Ref) -> Result<JsonValue> {
     }
 
     let target = target.fetch_channel().await?;
+    match target {
+        Channel::SavedMessages { .. }
+        | Channel::TextChannel { .. } => return Err(Error::CannotJoinCall),
+        _ => {}
+    }
+
     let perm = permissions::PermissionCalculator::new(&user)
         .with_channel(&target)
         .for_channel()