Search account domain in lowercase (#13016)

* Search account domain in lowercase

* fix rubocop error

* fix spec/models/account_spec.rb

spec/validators/unique_username_validator_spec.rb

@@ -4,22 +4,65 @@ require 'rails_helper'
 
 describe UniqueUsernameValidator do
   describe '#validate' do
+    context 'when local account' do
+      it 'does not add errors if username is nil' do
+        account = double(username: nil, domain: nil, persisted?: false, errors: double(add: nil))
+        subject.validate(account)
+        expect(account.errors).to_not have_received(:add)
+      end
+
+      it 'does not add errors when existing one is subject itself' do
+        account = Fabricate(:account, username: 'abcdef')
+        expect(account).to be_valid
+      end
+
+      it 'adds an error when the username is already used with ignoring cases' do
+        Fabricate(:account, username: 'ABCdef')
+        account = double(username: 'abcDEF', domain: nil, persisted?: false, errors: double(add: nil))
+        subject.validate(account)
+        expect(account.errors).to have_received(:add)
+      end
+
+      it 'does not add errors when same username remote account exists' do
+        Fabricate(:account, username: 'abcdef', domain: 'example.com')
+        account = double(username: 'abcdef', domain: nil, persisted?: false, errors: double(add: nil))
+        subject.validate(account)
+        expect(account.errors).to_not have_received(:add)
+      end
+    end
+  end
+
+  context 'when remote account' do
     it 'does not add errors if username is nil' do
-      account = double(username: nil, persisted?: false, errors: double(add: nil))
+      account = double(username: nil, domain: 'example.com', persisted?: false, errors: double(add: nil))
       subject.validate(account)
       expect(account.errors).to_not have_received(:add)
     end
 
     it 'does not add errors when existing one is subject itself' do
-      account = Fabricate(:account, username: 'abcdef')
+      account = Fabricate(:account, username: 'abcdef', domain: 'example.com')
       expect(account).to be_valid
     end
 
     it 'adds an error when the username is already used with ignoring cases' do
-      Fabricate(:account, username: 'ABCdef')
-      account = double(username: 'abcDEF', persisted?: false, errors: double(add: nil))
+      Fabricate(:account, username: 'ABCdef', domain: 'example.com')
+      account = double(username: 'abcDEF', domain: 'example.com', persisted?: false, errors: double(add: nil))
       subject.validate(account)
       expect(account.errors).to have_received(:add)
     end
+
+    it 'adds an error when the domain is already used with ignoring cases' do
+      Fabricate(:account, username: 'ABCdef', domain: 'example.com')
+      account = double(username: 'ABCdef', domain: 'EXAMPLE.COM', persisted?: false, errors: double(add: nil))
+      subject.validate(account)
+      expect(account.errors).to have_received(:add)
+    end
+
+    it 'does not add errors when account with the same username and another domain exists' do
+      Fabricate(:account, username: 'abcdef', domain: 'example.com')
+      account = double(username: 'abcdef', domain: 'example2.com', persisted?: false, errors: double(add: nil))
+      subject.validate(account)
+      expect(account.errors).to_not have_received(:add)
+    end
   end
 end