Add log formatter with option to only log report description (#62)

Author: sylane

README.md

@@ -195,6 +195,27 @@ You can copy paste these settings:
 ].
 ```
 
+To simplify the log on the device while still sending full log reports to
+griso.io, use grisp_connect_log log formatter with single-line in the default
+log handler:
+
+```
+            {handler, default, logger_std_h, #{
+                level => notice,
+                formatter => {grisp_connect_log, #{
+                    legacy_header => false,
+                    single_line => true,
+                    description_only => true
+                }},
+                filter_default => log,
+                filters => [
+                    % Filter out supervisor progress reports so TLS certificates
+                    % are not swamping the console if the level is set to info...
+                    {disable_progress, {fun logger_filters:progress/2, stop}}
+                ]
+            }}
+```
+
 ## Development
 
 ### Local Development

src/grisp_connect_log.erl

@@ -2,12 +2,18 @@
 %% @end
 -module(grisp_connect_log).
 
+-behaviour(logger_formatter).
+
 -include_lib("kernel/include/logger.hrl").
 
 % API functions
 -export([get/1]).
 -export([sync/1]).
 
+% Behaviour logger_formatter callback functions
+-export([check_config/1]).
+-export([format/2]).
+
 %--- Macros --------------------------------------------------------------------
 
 % FixMe:
@@ -45,6 +51,24 @@ sync(#{seq := Seq, dropped := Dropped}) ->
     grisp_connect_logger_bin:sync(Seq, Dropped).
 
 
+%--- Beahviour logger_formatter Callback Functions -----------------------------
+
+check_config(Config = #{description_only := Bool})
+  when is_boolean(Bool) ->
+    logger_formatter:check_config(maps:remove(description_only, Config));
+check_config(#{description_only := V}) ->
+    {error, {invalid_formatter_config, ?MODULE, {description_only, V}}};
+check_config(Config) ->
+    logger_formatter:check_config(Config).
+
+format(LogEvent = #{msg := {report, #{description := Desc}}},
+       Config = #{description_only := true}) when is_binary(Desc) ->
+    logger_formatter:format(LogEvent#{msg := {string, Desc}},
+                            maps:remove(description_only, Config));
+format(LogEvent, Config) ->
+    logger_formatter:format(LogEvent, maps:remove(description_only, Config)).
+
+
 %--- Internal Functions --------------------------------------------------------
 
 jsonify(Event) ->