Add branch_routing_enabled to Group

Add a new boolean column for enabling the branch_routing feature flag.

Author: thomasiles

db/migrate/20250124094215_add_branching_enabled_to_groups.rb

@@ -0,0 +1,5 @@
+class AddBranchingEnabledToGroups < ActiveRecord::Migration[8.0]
+  def change
+    add_column :groups, :branch_routing_enabled, :boolean, default: false
+  end
+end