Extracting i18n functionality to i18n core library (#16914)

* extracting i18n functionality to i18n core library

* Removing utils.T

* Adding documentation and changing one function name for better explanation

* Changing other missing utils.T

* Adding license string

* Renaming corelibs to pkg

* Renaming corelibs to pkg (moving directory)

* Renaming from pkg to shared

* Fixing bodyPage.Html casing

* Fixing merges

* Fixing merge problem

* Fixing tests

store/sqlstore/store.go

@@ -35,8 +35,8 @@ import (
 	"github.com/mattermost/mattermost-server/v5/einterfaces"
 	"github.com/mattermost/mattermost-server/v5/mlog"
 	"github.com/mattermost/mattermost-server/v5/model"
+	"github.com/mattermost/mattermost-server/v5/shared/i18n"
 	"github.com/mattermost/mattermost-server/v5/store"
-	"github.com/mattermost/mattermost-server/v5/utils"
 )
 
 type migrationDirection string
@@ -1322,7 +1322,7 @@ func (me mattermConverter) FromDb(target interface{}) (gorp.CustomScanner, bool)
 		binder := func(holder, target interface{}) error {
 			s, ok := holder.(*string)
 			if !ok {
-				return errors.New(utils.T("store.sql.convert_string_map"))
+				return errors.New(i18n.T("store.sql.convert_string_map"))
 			}
 			b := []byte(*s)
 			return json.Unmarshal(b, target)
@@ -1332,7 +1332,7 @@ func (me mattermConverter) FromDb(target interface{}) (gorp.CustomScanner, bool)
 		binder := func(holder, target interface{}) error {
 			s, ok := holder.(*string)
 			if !ok {
-				return errors.New(utils.T("store.sql.convert_string_map"))
+				return errors.New(i18n.T("store.sql.convert_string_map"))
 			}
 			b := []byte(*s)
 			return json.Unmarshal(b, target)
@@ -1342,7 +1342,7 @@ func (me mattermConverter) FromDb(target interface{}) (gorp.CustomScanner, bool)
 		binder := func(holder, target interface{}) error {
 			s, ok := holder.(*string)
 			if !ok {
-				return errors.New(utils.T("store.sql.convert_string_array"))
+				return errors.New(i18n.T("store.sql.convert_string_array"))
 			}
 			b := []byte(*s)
 			return json.Unmarshal(b, target)
@@ -1352,7 +1352,7 @@ func (me mattermConverter) FromDb(target interface{}) (gorp.CustomScanner, bool)
 		binder := func(holder, target interface{}) error {
 			s, ok := holder.(*string)
 			if !ok {
-				return errors.New(utils.T("store.sql.convert_string_interface"))
+				return errors.New(i18n.T("store.sql.convert_string_interface"))
 			}
 			b := []byte(*s)
 			return json.Unmarshal(b, target)
@@ -1362,7 +1362,7 @@ func (me mattermConverter) FromDb(target interface{}) (gorp.CustomScanner, bool)
 		binder := func(holder, target interface{}) error {
 			s, ok := holder.(*string)
 			if !ok {
-				return errors.New(utils.T("store.sql.convert_string_interface"))
+				return errors.New(i18n.T("store.sql.convert_string_interface"))
 			}
 			b := []byte(*s)
 			return json.Unmarshal(b, target)