code: public static AuthHandler credentials(String jwtFile, String nkeyFile) {
          return NatsImpl.credentials(jwtFile, nkeyFile);
      }
docs: Create an authhandler from a jwt file and an nkey file. The handler will read the files each time it needs to respond to a request
  and clear the memory after. This has a small price, but will only be encountered during connect or reconnect.
  
  @param jwtFile a file containing a user JWT, may or may not contain separators
  @param nkeyFile a file containing a user nkey that matches the JWT, may or may not contain separators
  @return an authhandler that will use the chain file to load/clear the nkey and jwt as needed