fix(logging): add line-break after each JSON log

src/emqx.app.src

@@ -1,7 +1,7 @@
 {application, emqx,
  [{id, "emqx"},
   {description, "EMQ X"},
-  {vsn, "4.3.0"}, % strict semver, bump manually!
+  {vsn, "4.3.1"}, % strict semver, bump manually!
   {modules, []},
   {registered, []},
   {applications, [kernel,stdlib,gproc,gen_rpc,esockd,cowboy,sasl,os_mon]},

src/emqx.appup.src

@@ -1,9 +1,14 @@
 %% -*-: erlang -*-
 {VSN,
- [
+ [ {"4.3.0",
+    [ {load_module, emqx_logger_jsonfmt, brutal_purge, soft_purge, []}
+    ]},
    {<<".*">>, []}
  ],
  [
+   {"4.3.0",
+    [ {load_module, emqx_logger_jsonfmt, brutal_purge, soft_purge, []}
+    ]},
    {<<".*">>, []}
  ]
 }.

src/emqx_logger_jsonfmt.erl

@@ -48,7 +48,7 @@
 -spec format(logger:log_event(), config()) -> iodata().
 format(#{level := Level, msg := Msg, meta := Meta}, Config0) when is_map(Config0) ->
     Config = add_default_config(Config0),
-    format(Msg, Meta#{level => Level}, Config).
+    [format(Msg, Meta#{level => Level}, Config) , "\n"].
 
 format(Msg, Meta, Config) ->
     Data0 =