Structured logging (#8673)

* Implementing structured logging

* Changes to en.json to allow refactor to run.

* Fixing global logger

* Structured logger initalization.

* Add caller.

* Do some log redirection.

* Auto refactor

* Cleaning up l4g reference and removing dependancy.

* Removing junk.

* Copyright headers.

* Fixing tests

* Revert "Changes to en.json to allow refactor to run."

This reverts commit fd8249e99bcad0231e6ea65cd77c32aae9a54026.

* Fixing some auto refactor strangeness and typo.

* Making keys more human readable.

api/api.go

@@ -6,9 +6,9 @@ package api
 import (
 	"net/http"
 
-	l4g "github.com/alecthomas/log4go"
 	"github.com/gorilla/mux"
 	"github.com/mattermost/mattermost-server/app"
+	"github.com/mattermost/mattermost-server/mlog"
 	"github.com/mattermost/mattermost-server/model"
 
 	_ "github.com/nicksnyder/go-i18n/i18n"
@@ -114,7 +114,7 @@ func Init(a *app.App, root *mux.Router) *API {
 	a.InitEmailBatching()
 
 	if *a.Config().ServiceSettings.EnableAPIv3 {
-		l4g.Info("API version 3 is scheduled for deprecation. Please see https://api.mattermost.com for details.")
+		mlog.Info("API version 3 is scheduled for deprecation. Please see https://api.mattermost.com for details.")
 	}
 
 	return api