Add `sanitize_name` helper to sanitize URLs in user full name

app/helpers/emails_helper.rb

@@ -36,6 +36,14 @@ module EmailsHelper
     nil
   end
 
+  def sanitize_name(name)
+    if name =~ URI::DEFAULT_PARSER.regexp[:URI_REF]
+      name.tr('.', '_')
+    else
+      name
+    end
+  end
+
   def password_reset_token_valid_time
     valid_hours = Devise.reset_password_within / 60 / 60
     if valid_hours >= 24

spec/helpers/emails_helper_spec.rb

 require 'spec_helper'
 
 describe EmailsHelper do
+  describe 'sanitize_name' do
+    context 'when name contains a valid URL string' do
+      it 'returns name with `.` replaced with `_` to prevent mail clients from auto-linking URLs' do
+        expect(sanitize_name('https://about.gitlab.com')).to eq('https://about_gitlab_com')
+        expect(sanitize_name('www.gitlab.com')).to eq('www_gitlab_com')
+        expect(sanitize_name('//about.gitlab.com/handbook/security/#best-practices')).to eq('//about_gitlab_com/handbook/security/#best-practices')
+      end
+
+      it 'returns name as it is when it does not contain a URL' do
+        expect(sanitize_name('Foo Bar')).to eq('Foo Bar')
+      end
+    end
+  end
+
   describe 'password_reset_token_valid_time' do
     def validate_time_string(time_limit, expected_string)
       Devise.reset_password_within = time_limit