title: Firebase User Object is null on Localhost
body: <p>I am having an issue with Firebase tokens on localhost.</p>
  
  <pre><code>@Api(name = "account",
   version = "v1",
   authenticators =  {EspAuthenticator.class},
   issuers =        {@ApiIssuer(  name = "firebase",
                                  issuer =     "https://securetoken.google.com/PROJECTID",
                                  jwksUri =     "https://www.googleapis.com/service_accounts/v1/metadata/x509/securetoken@system.gserviceaccount.com")},
   issuerAudiences = {@ApiIssuerAudience(name = "firebase", audiences =     {"PROJECTID"})})             
  public class AccountService {
  
      @ApiMethod(path="user/{id}", httpMethod = "get")
      public User GetUser(@Named("id") String id, User user) throws UnauthorizedException,BadRequestException,NotFoundException    
      {
      }
  }
  </code></pre>
  
  <p>In particular the User user which should return com.google.api.server.spi.auth.common.User. 
  When I run this on google cloud then I get returned the correct result.</p>
  
  <p>When I run this on localhost it always returns null.</p>
  
  <p>I can't figure out what I am doing wrong as Localhost should be ok with firebase by default as shown below. Why cannot I not see the user object on localhost?</p>
  
  <p><a href="https://i.stack.imgur.com/k6hVv.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/k6hVv.png" alt="enter image description here"></a></p>