Isolate more the mfa service (#16925)

* Isolate more the mfa service

* Simplifing the mfa service

* Removing channels and adding waitgroup

* Migrating mfa service to regular errors

* Fixing tests

* i18n extract

* Addressing PR review comments

* Removing unneeded struct

model/utils_test.go

@@ -5,7 +5,6 @@ package model
 
 import (
 	"bytes"
-	"encoding/base32"
 	"fmt"
 	"net/http"
 	"reflect"
@@ -32,13 +31,6 @@ func TestRandomString(t *testing.T) {
 	}
 }
 
-func TestRandomBase32String(t *testing.T) {
-	for i := 0; i < 1000; i++ {
-		str := NewRandomBase32String(i)
-		require.Len(t, str, base32.StdEncoding.EncodedLen(i))
-	}
-}
-
 func TestGetMillisForTime(t *testing.T) {
 	thisTimeMillis := int64(1471219200000)
 	thisTime := time.Date(2016, time.August, 15, 0, 0, 0, 0, time.UTC)