config-servlet/src/main/java/org/ocpsoft/rewrite/servlet/config/Header.java
public static Header exists(final String name)
   {
      return new Header(name, "{" + Header.class.getName() + "_value}") {
         @Override
         public String toString()
         {
            return "Header.exists(\"" + name + "\")";
         }
      };
   }
public static Header exists(final String name)
   {
      return new Header(name, "{" + Header.class.getName() + "_value}") {
         @Override
         public String toString()
         {
            return "Header.exists(\"" + name + "\")";
         }
      };
   }
Create a {@link Header} condition that matches only against the existence of a header with a name matching the
given pattern. The header value is ignored.
<p>
The given name pattern may be parameterized:
<p>
<code>
Header.exists("Accept-Encoding")<br>
Header.exists("Accept-{acceptType}")<br>
Header.exists("{anything}")<br>
...
</code>
<p>

@see {@link ConfigurationRuleParameterBuilder#where(String) {@link HttpServletRequest#getHeader(String)}

@param name {@link ParameterizedPattern} matching the header name.