Make user constrainer lookup same as controller and add more constrainer tests

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

lib/constraints/user_url_constrainer.rb

@@ -2,6 +2,6 @@ require 'constraints/namespace_url_constrainer'
 
 class UserUrlConstrainer < NamespaceUrlConstrainer
   def find_resource(id)
-    User.find_by_username(id)
+    User.find_by('lower(username) = ?', id.downcase)
   end
 end

spec/lib/constraints/group_url_constrainer_spec.rb

@@ -0,0 +1,10 @@
+require 'spec_helper'
+
+describe GroupUrlConstrainer, lib: true do
+  let!(:username) { create(:group, path: 'gitlab-org') }
+
+  describe '#find_resource' do
+    it { expect(!!subject.find_resource('gitlab-org')).to be_truthy }
+    it { expect(!!subject.find_resource('gitlab-com')).to be_falsey }
+  end
+end

spec/lib/constraints/namespace_url_constrainer_spec.rb

@@ -2,7 +2,6 @@ require 'spec_helper'
 
 describe NamespaceUrlConstrainer, lib: true do
   let!(:group) { create(:group, path: 'gitlab') }
-  subject { NamespaceUrlConstrainer.new }
 
   describe '#matches?' do
     context 'existing namespace' do

spec/lib/constraints/user_url_constrainer_spec.rb

@@ -0,0 +1,10 @@
+require 'spec_helper'
+
+describe UserUrlConstrainer, lib: true do
+  let!(:username) { create(:user, username: 'dz') }
+
+  describe '#find_resource' do
+    it { expect(!!subject.find_resource('dz')).to be_truthy }
+    it { expect(!!subject.find_resource('john')).to be_falsey }
+  end
+end