chore: Generate test data for bulk insertion (#11229)

Co-authored-by: Vishnu Narayanan <vishnu@chatwoot.com>
Co-authored-by: Sojan <sojan@pepalo.com>
Co-authored-by: tds-1 <tanmay@qoala.id>
Co-authored-by: Shivam Mishra <scm.mymail@gmail.com>

lib/test_data/display_id_tracker.rb

@@ -0,0 +1,12 @@
+class TestData::DisplayIdTracker
+  attr_reader :current
+
+  def initialize(account:)
+    max_display_id = Conversation.where(account_id: account.id).maximum(:display_id) || 0
+    @current = max_display_id
+  end
+
+  def next_id
+    @current += 1
+  end
+end