[Statsig] Track threads (#6057)

* [Statsig] Send thread length

* Split events

src/lib/statsig/events.ts

@@ -122,11 +122,16 @@ export type LogEvents = {
   'post:create': {
     imageCount: number
     isReply: boolean
+    isPartOfThread: boolean
     hasLink: boolean
     hasQuote: boolean
     langs: string
     logContext: 'Composer'
   }
+  'thread:create': {
+    postCount: number
+    isReply: boolean
+  }
   'post:like:sampled': {
     doesLikerFollowPoster: boolean | undefined
     doesPosterFollowLiker: boolean | undefined

src/view/com/composer/Composer.tsx

@@ -405,6 +405,7 @@ export const ComposePost = ({
                 ? post.embed.media.images.length
                 : 0,
             isReply: index > 0 || !!replyTo,
+            isPartOfThread: thread.posts.length > 1,
             hasLink: !!post.embed.link,
             hasQuote: !!post.embed.quote,
             langs: langPrefs.postLanguage,
@@ -413,6 +414,12 @@ export const ComposePost = ({
           index++
         }
       }
+      if (thread.posts.length > 1) {
+        logEvent('thread:create', {
+          postCount: thread.posts.length,
+          isReply: !!replyTo,
+        })
+      }
     }
     if (postUri && !replyTo) {
       emitPostCreated()