Same as start_link([]).
Start and link to calling process.
-callback clients(term()) -> term().
-callback download_artifact(term(), node()) -> term().
-callback servers(term()) -> term().
-callback upload_artifact(term(), node(), term()) -> term().
-spec nodes() -> {ok, [node()]}.
-spec servers() -> {ok, [node()]}.
-spec start_link() -> {ok, pid()} | ignore | {error, term()}.
-spec start_link(list()) -> {ok, pid()} | ignore | {error, term()}.