code: public static String prefixFromPlainForceHttp(String u) {
          u = SURT.prefixFromPlain(u);
          u = coerceFromHttpsForComparison(u);
          return u;
      }
docs: Given a plain URI or hostname/hostname+path, deduce an implied SURT
  prefix from it. Results may be unpredictable on strings that cannot
  be interpreted as URIs.
  
  UURI 'fixup' is applied to the URI that is built.
  
  HTTPS URIs are changed to HTTP as a convenience for the usual
  preferred common-treatment.
  
  @param u URI or almost-URI to consider
  @return implied SURT prefix form