chore: Automate SSL with Cloudflare (#12021)

This PR adds support for automatic SSL issuance using Cloudflare when a
custom domain is updated.

- Introduced a cloudflare configuration. If present, the system will
attempt to issue an SSL certificate via Cloudflare whenever a custom
domain is added or changed.
- SSL verification is handled using an HTTP challenge.
- The job will store the HTTP challenge response provided by Cloudflare
and serve it under the /.well-known/cf path automatically.

How to test:

- Create a Cloudflare zone for your domain and copy the Zone ID.
- Generate a Cloudflare API token with the required SSL certificate
permissions.
- Set the Fallback Origin under SSL -> Custom HostName to the Chatwoot
installation.
- Add or update a custom domain and verify that the SSL certificate is
automatically issued.

---------

Co-authored-by: Sojan Jose <sojan@pepalo.com>

enterprise/app/models/enterprise/concerns/portal.rb

@@ -0,0 +1,14 @@
+module Enterprise::Concerns::Portal
+  extend ActiveSupport::Concern
+
+  included do
+    after_save :enqueue_cloudflare_verification, if: :saved_change_to_custom_domain?
+  end
+
+  def enqueue_cloudflare_verification
+    return if custom_domain.blank?
+    return unless ChatwootApp.chatwoot_cloud?
+
+    Enterprise::CloudflareVerificationJob.perform_later(id)
+  end
+end