Be more permissive with email address validation: it only has to contain an '@'

Fixes #3851

CHANGELOG

@@ -15,6 +15,7 @@ v 8.5.0 (unreleased)
   - Whitelist raw "abbr" elements when parsing Markdown (Benedict Etzel)
   - Fix label links for a merge request pointing to issues list
   - Don't vendor minified JS
+  - Be more permissive with email address validation: it only has to contain an '@' (Calum Robinson)
   - Display 404 error on group not found
   - Track project import failure
   - Support Two-factor Authentication for LDAP users

app/validators/email_validator.rb

@@ -8,7 +8,7 @@
 # See http://www.remote.org/jochen/mail/info/chars.html
 #
 class EmailValidator < ActiveModel::EachValidator
-  PATTERN = /\A\s*([-a-z0-9+._']{1,64})@((?:[-a-z0-9]+\.)+[a-z]{2,})\s*\z/i.freeze
+  PATTERN = /@/.freeze
   def validate_each(record, attribute, value)
     unless value =~ PATTERN

spec/models/user_spec.rb

@@ -140,14 +140,14 @@ describe User, models: true do
         expect(user).to be_invalid
       end
-      it 'rejects mailto:test@example.com' do
+      it 'accepts mailto:test@example.com' do
         user = build(:user, email: 'mailto:test@example.com')
-        expect(user).to be_invalid
+        expect(user).to be_valid
       end
-      it "rejects lol!'+=?><#$%^&*()@gmail.com" do
+      it "accepts lol!'+=?><#$%^&*()@gmail.com" do
         user = build(:user, email: "lol!'+=?><#$%^&*()@gmail.com")
-        expect(user).to be_invalid
+        expect(user).to be_valid
       end
       context 'when no signup domains listed' do