code: public JwkProviderBuilder cached(long cacheSize, long expiresIn, TimeUnit unit) {
          this.cached = true;
          this.cacheSize = cacheSize;
          this.expiresIn = expiresIn;
          this.expiresUnit = unit;
          return this;
      }
docs: Enable the cache specifying size and expire time.
  
  @param cacheSize number of jwk to cache
  @param expiresIn amount of time the jwk will be cached
  @param unit      unit of time for the expire of jwk
  @return the builder