chore: Increase character limit for external url fields (#7230)

- Increase the external url field validation to 2048 characters

fixes: https://github.com/chatwoot/chatwoot/issues/7098

spec/models/channel/api_spec.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe Channel::Api do
+  # This validation happens in ApplicationRecord
+  describe 'length validations' do
+    let(:channel_api) { create(:channel_api) }
+
+    context 'when it validates webhook_url length' do
+      it 'valid when within limit' do
+        channel_api.webhook_url = 'a' * Limits::URL_LENGTH_LIMIT
+        expect(channel_api.valid?).to be true
+      end
+
+      it 'invalid when crossed the limit' do
+        channel_api.webhook_url = 'a' * (Limits::URL_LENGTH_LIMIT + 1)
+        channel_api.valid?
+        expect(channel_api.errors[:webhook_url]).to include("is too long (maximum is #{Limits::URL_LENGTH_LIMIT} characters)")
+      end
+    end
+  end
+end