Add min_trust_to_create_topic setting to require a certain trust level before users can start new topics

spec/components/guardian_spec.rb

@@ -283,6 +283,21 @@ describe Guardian do
         category.save
         Guardian.new(user).can_create?(Topic,category).should be_false
       end
+
+      it "is true for new users by default" do
+        Guardian.new(user).can_create?(Topic,Fabricate(:category)).should be_true
+      end
+
+      it "is false if user has not met minimum trust level" do
+        SiteSetting.stubs(:min_trust_to_create_topic).returns(1)
+        Guardian.new(build(:user, trust_level: 0)).can_create?(Topic,Fabricate(:category)).should be_false
+      end
+
+      it "is true if user has met or exceeded the minimum trust level" do
+        SiteSetting.stubs(:min_trust_to_create_topic).returns(1)
+        Guardian.new(build(:user, trust_level: 1)).can_create?(Topic,Fabricate(:category)).should be_true
+        Guardian.new(build(:user, trust_level: 2)).can_create?(Topic,Fabricate(:category)).should be_true
+      end
     end
 
     describe 'a Post' do