events: Add Thread::without_fallback

There was no constructor that initializes the minimal set of required
fields previously.

crates/ruma-events/CHANGELOG.md

@@ -1,5 +1,10 @@
 # [unreleased]
 
+Improvements:
+
+- Add `Thread::without_fallback` as a constructor that initializes the minimal
+  set of required fields
+
 # 0.27.3
 
 Improvements:

crates/ruma-events/src/relation.rs

@@ -113,6 +113,12 @@ impl Thread {
         Self { event_id, in_reply_to: Some(InReplyTo::new(latest_event_id)), is_falling_back: true }
     }
 
+    /// Convenience method to create a regular `Thread` relation with the given root event ID and
+    /// *without* the recommended reply fallback.
+    pub fn without_fallback(event_id: OwnedEventId) -> Self {
+        Self { event_id, in_reply_to: None, is_falling_back: false }
+    }
+
     /// Convenience method to create a reply `Thread` relation with the given root event ID and
     /// replied-to event ID.
     pub fn reply(event_id: OwnedEventId, reply_to_event_id: OwnedEventId) -> Self {