code: public boolean supports(final WebContext ctx) {
          return AWS_AUTH4_PATTERN.matcher(ctx.getHeaderValue("Authorization").asString("")).matches()
                 || X_AMZ_CREDENTIAL_PATTERN.matcher(ctx.get("X-Amz-Credential").asString("")).matches();
      }
docs: Determines if the given request contains an AWS4 auth token.
  
  @param ctx the request to check
  @return <tt>true</tt> if the request contains an AWS4 auth token, <tt>false</tt>  otherwise.