FEATURE: Hidden site setting for max username length

app/assets/javascripts/discourse/templates/user/username.js.handlebars

@@ -18,7 +18,7 @@
     <div class="control-group">
       <label class="control-label">{{i18n user.username.title}}</label>
       <div class="controls">
-        {{textField value=newUsername id="change_username" classNames="input-xxlarge" maxlength="15"}}
+        {{textField value=newUsername id="change_username" classNames="input-xxlarge" maxlengthBinding="Discourse.SiteSettings.max_username_length"}}
       </div>
       <div class='instructions'>
         {{#if taken}}

app/models/user.rb

@@ -102,7 +102,7 @@ class User < ActiveRecord::Base
     if SiteSetting.enforce_global_nicknames
       GLOBAL_USERNAME_LENGTH_RANGE
     else
-      SiteSetting.min_username_length.to_i..GLOBAL_USERNAME_LENGTH_RANGE.end
+      SiteSetting.min_username_length.to_i..SiteSetting.max_username_length.to_i
     end
   end
 

config/site_settings.yml

@@ -103,6 +103,10 @@ users:
   min_username_length:
     client: true
     default: 3
+  max_username_length:
+    client: true
+    default: 15
+    hidden: true
   min_password_length:
     client: true
     default: 8