class ActiveStorage::Service

def url(key, expires_in:, disposition:, filename:, content_type:)

+filename+, and +content_type+ that you wish the file to be served with on request.
of seconds specified in +expires_in+. You most also provide the +disposition+ (+:inline+ or +:attachment+),
Returns a signed, temporary URL for the file at the +key+. The URL will be valid for the amount 
def url(key, expires_in:, disposition:, filename:, content_type:)
  raise NotImplementedError
end