def register(name, other = Chain::EMPTY, exception_chain = Chain::EMPTY, &block)
      actions[name] = chain(name, other, exception_chain, &block)
      self
    end
def register(name, other = Chain::EMPTY, exception_chain = Chain::EMPTY, &block)
      actions[name] = chain(name, other, exception_chain, &block)
      self
    end
Register a new chain under the given +name+

 @param [#to_sym] name
   the new chain's name

 @param [Chain] other
   the chain to build on top of

 @param [Chain] exception_chain
   the chain to invoke in case of uncaught exceptions in handlers

 @return [Chain]
   the registered chain

 @api private