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.

api4/user.go

@@ -9,8 +9,8 @@ import (
 	"strconv"
 	"time"
 
-	l4g "github.com/alecthomas/log4go"
 	"github.com/mattermost/mattermost-server/app"
+	"github.com/mattermost/mattermost-server/mlog"
 	"github.com/mattermost/mattermost-server/model"
 	"github.com/mattermost/mattermost-server/store"
 )
@@ -1177,7 +1177,7 @@ func sendVerificationEmail(c *Context, w http.ResponseWriter, r *http.Request) {
 	err = c.App.SendEmailVerification(user)
 	if err != nil {
 		// Don't want to leak whether the email is valid or not
-		l4g.Error(err.Error())
+		mlog.Error(err.Error())
 		ReturnStatusOK(w)
 		return
 	}