Fix call to atom_to_binary/1 for Erlang/OTP older than 23

src/ejabberd_admin.erl

@@ -869,7 +869,7 @@ join_cluster_here(_Node, _IsNodes, true, _Ping) ->
 join_cluster_here(_Node, _IsNodes, _IsKnownNodes, pang) ->
     {error, "This node cannot reach that node."};
 join_cluster_here(Node, false, false, pong) ->
-    case ejabberd_cluster:call(Node, ejabberd_admin, join_cluster, [atom_to_binary(node())]) of
+    case ejabberd_cluster:call(Node, ejabberd_admin, join_cluster, [misc:atom_to_binary(node())]) of
         {ok, _} ->
             {ok, "Trying to join node to this cluster, wait a few seconds and check the list of nodes."};
         Error ->

src/ejabberd_web_admin.erl

@@ -1607,7 +1607,7 @@ make_login_items(#request{us = {Username, Host}} = R, Level) ->
               ?LI([?C(unicode:characters_to_binary("🏭")),
                    make_command(echo,
                                 R,
-                                [{<<"sentence">>, atom_to_binary(node())}],
+                                [{<<"sentence">>, misc:atom_to_binary(node())}],
                                 [{only, value},
                                  {result_links, [{sentence, node, Level, <<"">>}]}])]),
               ?LI([?C(unicode:characters_to_binary("📤")),

src/misc.erl

@@ -316,6 +316,9 @@ binary_to_atom(Bin) ->
 tuple_to_binary(T) ->
     iolist_to_binary(tuple_to_list(T)).
 
+%% erlang:atom_to_binary/1 is available since OTP 23
+%% https://www.erlang.org/doc/apps/erts/erlang#atom_to_binary/1
+%% Let's use /2 for backwards compatibility.
 atom_to_binary(A) ->
     erlang:atom_to_binary(A, utf8).