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

app/models/min_trust_to_create_topic_setting.rb

@@ -0,0 +1,18 @@
+require_dependency 'enum_site_setting'
+
+class MinTrustToCreateTopicSetting < EnumSiteSetting
+
+  def self.valid_value?(val)
+    valid_values.any? { |v| v.to_s == val.to_s }
+  end
+
+  def self.values
+    @values ||= valid_values.map {|x| {name: x.to_s, value: x} }
+  end
+
+  private
+
+  def self.valid_values
+    TrustLevel.levels.values.sort
+  end
+end

app/models/site_setting.rb

@@ -205,6 +205,8 @@ class SiteSetting < ActiveRecord::Base
   setting(:regular_requires_likes_given, 1)
   setting(:regular_requires_topic_reply_count, 3)
 
+  setting(:min_trust_to_create_topic, 0, enum: 'MinTrustToCreateTopicSetting')
+
   # Reply by Email Settings
   setting(:reply_by_email_enabled, false)
   setting(:reply_by_email_address, '')