code: public String computeHash(WebContext ctx, String pathPrefix) {
          try {
              return doComputeHash(ctx, pathPrefix);
          } catch (Exception e) {
              throw Exceptions.handle(UserContext.LOG, e);
          }
      }
docs: Computes the authentication hash as specified by the AWS SDK for verification purposes.
  
  @param ctx        the current request to fetch parameters from
  @param pathPrefix the path prefix to append to the current uri
  @return the computes hash value