Add SMTP timeout configuration options

In https://github.com/mikel/mail/pull/1427/files, mail v2.8.1 gem
modified the default open and read timeout values to 5 seconds instead
of the default `Net::SMTP` 30 and 60 seconds, respectively.

Since upgrading to GitLab 15.10.3, some users have observed receiving
`Net::ReadTimeout` errors. This commit restores the original defaults
and allows users to configure the timeouts.

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/410336

Changelog: added

files/gitlab-cookbooks/gitlab/attributes/default.rb

@@ -506,6 +506,8 @@ default['gitlab']['gitlab-rails']['smtp_pool'] = false
 # Path to the public Certificate Authority file
 # defaults to /opt/gitlab/embedded/ssl/certs/cacert.pem. The install-dir path is set at build time
 default['gitlab']['gitlab-rails']['smtp_ca_file'] = "#{node['package']['install-dir']}/embedded/ssl/certs/cacert.pem"
+default['gitlab']['gitlab-rails']['smtp_open_timeout'] = 30
+default['gitlab']['gitlab-rails']['smtp_read_timeout'] = 60
 # Path to directory that contains (ca) certificates that should also be trusted (e.g. on
 # outgoing Webhooks connections). For these certificates symlinks will be created in

files/gitlab-cookbooks/gitlab/templates/default/smtp_settings.rb.erb

@@ -10,7 +10,7 @@ if Rails.env.production?
     <% end %>
     user_name: <%= node['gitlab']['gitlab-rails']["smtp_user_name"]&.inspect || "secrets.username" %>,
     password: <%= node['gitlab']['gitlab-rails']["smtp_password"]&.inspect || "secrets.password"  %>,
-<% %w{ address port domain enable_starttls_auto tls ssl openssl_verify_mode ca_path ca_file }.each do |key| %>
+<% %w{ address port domain enable_starttls_auto tls ssl openssl_verify_mode ca_path ca_file open_timeout read_timeout }.each do |key| %>
   <% value = node['gitlab']['gitlab-rails']["smtp_#{key}"] %>
     <%= "#{key}: #{value.inspect}," unless value.nil? %>
 <% end %>

spec/chef/cookbooks/gitlab/recipes/gitlab-rails_spec.rb

@@ -1196,6 +1196,56 @@ RSpec.describe 'gitlab::gitlab-rails' do
   end
   context 'SMTP settings' do
+    context 'defaults' do
+      before do
+        stub_gitlab_rb(
+          gitlab_rails: {
+            smtp_enable: true
+          }
+        )
+      end
+
+      it 'renders the default timeout values' do
+        expect(chef_run).to create_templatesymlink('Create a smtp_settings.rb and create a symlink to Rails root').with_variables(
+          hash_including(
+            'smtp_open_timeout' => 30,
+            'smtp_read_timeout' => 60
+          )
+        )
+
+        expect(chef_run).to render_file('/var/opt/gitlab/gitlab-rails/etc/smtp_settings.rb').with_content { |content|
+          expect(content).to include('open_timeout: 30')
+          expect(content).to include('read_timeout: 60')
+        }
+      end
+    end
+
+    context 'when timeouts are set' do
+      before do
+        stub_gitlab_rb(
+          gitlab_rails: {
+            smtp_enable: true,
+            smtp_open_timeout: 10,
+            smtp_read_timeout: 20
+          }
+        )
+      end
+
+      it 'renders the timeout values' do
+        expect(chef_run).to create_templatesymlink('Create a smtp_settings.rb and create a symlink to Rails root').with_variables(
+          hash_including(
+            'smtp_open_timeout' => 10,
+            'smtp_read_timeout' => 20
+          )
+        )
+
+        expect(chef_run).to render_file('/var/opt/gitlab/gitlab-rails/etc/smtp_settings.rb').with_content { |content|
+          expect(content).to include('open_timeout: 10')
+          expect(content).to include('read_timeout: 20')
+        }
+      end
+    end
+
     context 'when connection pooling is not configured' do
       it 'creates smtp_settings.rb with pooling disabled' do
         stub_gitlab_rb(