[CR-458] Enhance Logs Endpoint Message (#12984)

* Make it possible to identify log entries created via the post API endpoints

* Clarify wording

api4/system.go

@@ -262,14 +262,16 @@ func postLog(c *Context, w http.ResponseWriter, r *http.Request) {
 		msg = msg[0:399]
 	}
 
+	msg = "Client Logs API Endpoint Message: " + msg
+	fields := []mlog.Field{
+		mlog.String("type", "client_message"),
+		mlog.String("user_agent", c.App.UserAgent),
+	}
+
 	if !forceToDebug && lvl == "ERROR" {
-		err := &model.AppError{}
-		err.Message = msg
-		err.Id = msg
-		err.Where = "client"
-		c.LogError(err)
+		mlog.Error(msg, fields...)
 	} else {
-		mlog.Debug("message", mlog.String("message", msg))
+		mlog.Debug(msg, fields...)
 	}
 
 	m["message"] = msg

api4/system_test.go

@@ -283,6 +283,13 @@ func TestPostLog(t *testing.T) {
 	_, resp := Client.PostLog(message)
 	CheckNoError(t, resp)
 
+	*th.App.Config().ServiceSettings.EnableDeveloper = false
+
+	_, resp = Client.PostLog(message)
+	CheckNoError(t, resp)
+
+	*th.App.Config().ServiceSettings.EnableDeveloper = true
+
 	Client.Logout()
 
 	_, resp = Client.PostLog(message)