code: public <T> RestBuilder addProvider(Class<T> clazz, Class<? extends ContextProvider<T>> provider) {
  
  		Assert.notNull(clazz, "Missing provided class type!");
  		Assert.notNull(provider, "Missing context provider!");
  		registeredProviders.put(clazz, provider);
  		return this;
  	}
docs: Creates a provider that delivers type when needed
  @param provider to be executed when needed
  @param <T> provided object as argument
  @return builder