Reference to a named listener/endpoint exposed by a HostKit service.
@type t() :: %HostKit.Endpoint{ health: String.t() | nil, host: String.t() | nil, meta: map(), name: atom() | String.t(), port: pos_integer() | nil, protocol: atom() | nil, service: atom() | String.t() }
@spec declaration( atom() | String.t(), keyword() ) :: t()
@spec new(atom() | String.t(), atom() | String.t(), keyword()) :: t()
@spec resolved?(t()) :: boolean()
@spec upstream(t()) :: String.t()
@spec url(t()) :: String.t()