Implement offline POST method for starting an offline participation

db/migrate/20251030094151_add_name_to_offline.rb

@@ -0,0 +1,5 @@
+class AddNameToOffline < ActiveRecord::Migration[8.0]
+  def change
+    add_column :offlines, :name, :string, null: false
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2025_10_30_092221) do
+ActiveRecord::Schema[8.0].define(version: 2025_10_30_094151) do
   create_table "active_storage_attachments", force: :cascade do |t|
     t.string "name", null: false
     t.string "record_type", null: false
@@ -132,6 +132,7 @@ ActiveRecord::Schema[8.0].define(version: 2025_10_30_092221) do
     t.integer "contest_id", null: false
     t.datetime "start_time", null: false
     t.datetime "end_time"
+    t.string "name", null: false
     t.index ["contest_id"], name: "index_offlines_on_contest_id"
   end