feat: Added Instagram channel migration (#11181)

This PR is part of https://github.com/chatwoot/chatwoot/pull/11054 to
make the review cycle easier.

spec/factories/channel/channel_instagram.rb

@@ -0,0 +1,13 @@
+FactoryBot.define do
+  factory :channel_instagram, class: 'Channel::Instagram' do
+    account
+    access_token { SecureRandom.hex(32) }
+    instagram_id { SecureRandom.hex(16) }
+    expires_at { 60.days.from_now }
+    updated_at { 25.hours.ago }
+
+    after(:create) do |channel|
+      create(:inbox, channel: channel, account: channel.account)
+    end
+  end
+end

spec/models/channel/instagram_spec.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe Channel::Instagram do
+  let(:channel) { create(:channel_instagram) }
+
+  it { is_expected.to validate_presence_of(:account_id) }
+  it { is_expected.to validate_presence_of(:access_token) }
+  it { is_expected.to validate_presence_of(:instagram_id) }
+  it { is_expected.to belong_to(:account) }
+  it { is_expected.to have_one(:inbox).dependent(:destroy_async) }
+
+  it 'has a valid name' do
+    expect(channel.name).to eq('Instagram')
+  end
+end