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

model/command_args.go

@@ -7,21 +7,21 @@ import (
 	"encoding/json"
 	"io"
 
-	goi18n "github.com/mattermost/go-i18n/i18n"
+	"github.com/mattermost/mattermost-server/v5/shared/i18n"
 )
 
 type CommandArgs struct {
-	UserId          string               `json:"user_id"`
-	ChannelId       string               `json:"channel_id"`
-	TeamId          string               `json:"team_id"`
-	RootId          string               `json:"root_id"`
-	ParentId        string               `json:"parent_id"`
-	TriggerId       string               `json:"trigger_id,omitempty"`
-	Command         string               `json:"command"`
-	SiteURL         string               `json:"-"`
-	T               goi18n.TranslateFunc `json:"-"`
-	UserMentions    UserMentionMap       `json:"-"`
-	ChannelMentions ChannelMentionMap    `json:"-"`
+	UserId          string             `json:"user_id"`
+	ChannelId       string             `json:"channel_id"`
+	TeamId          string             `json:"team_id"`
+	RootId          string             `json:"root_id"`
+	ParentId        string             `json:"parent_id"`
+	TriggerId       string             `json:"trigger_id,omitempty"`
+	Command         string             `json:"command"`
+	SiteURL         string             `json:"-"`
+	T               i18n.TranslateFunc `json:"-"`
+	UserMentions    UserMentionMap     `json:"-"`
+	ChannelMentions ChannelMentionMap  `json:"-"`
 
 	// DO NOT USE Session field is deprecated. MM-26398
 	Session Session `json:"-"`

model/utils.go

@@ -22,7 +22,7 @@ import (
 	"time"
 	"unicode"
 
-	goi18n "github.com/mattermost/go-i18n/i18n"
+	"github.com/mattermost/mattermost-server/v5/shared/i18n"
 	"github.com/pborman/uuid"
 )
 
@@ -73,10 +73,10 @@ func (sa StringArray) Equals(input StringArray) bool {
 	return true
 }
 
-var translateFunc goi18n.TranslateFunc
+var translateFunc i18n.TranslateFunc
 var translateFuncOnce sync.Once
 
-func AppErrorInit(t goi18n.TranslateFunc) {
+func AppErrorInit(t i18n.TranslateFunc) {
 	translateFuncOnce.Do(func() {
 		translateFunc = t
 	})
@@ -97,7 +97,7 @@ func (er *AppError) Error() string {
 	return er.Where + ": " + er.Message + ", " + er.DetailedError
 }
 
-func (er *AppError) Translate(T goi18n.TranslateFunc) {
+func (er *AppError) Translate(T i18n.TranslateFunc) {
 	if T == nil {
 		er.Message = er.Id
 		return
@@ -110,7 +110,7 @@ func (er *AppError) Translate(T goi18n.TranslateFunc) {
 	}
 }
 
-func (er *AppError) SystemMessage(T goi18n.TranslateFunc) string {
+func (er *AppError) SystemMessage(T i18n.TranslateFunc) string {
 	if er.params == nil {
 		return T(er.Id)
 	}

model/websocket_request.go

@@ -7,7 +7,7 @@ import (
 	"encoding/json"
 	"io"
 
-	goi18n "github.com/mattermost/go-i18n/i18n"
+	"github.com/mattermost/mattermost-server/v5/shared/i18n"
 )
 
 // WebSocketRequest represents a request made to the server through a websocket.
@@ -18,9 +18,9 @@ type WebSocketRequest struct {
 	Data   map[string]interface{} `json:"data"`   // The metadata for an action.
 
 	// Server-provided fields
-	Session Session              `json:"-"`
-	T       goi18n.TranslateFunc `json:"-"`
-	Locale  string               `json:"-"`
+	Session Session            `json:"-"`
+	T       i18n.TranslateFunc `json:"-"`
+	Locale  string             `json:"-"`
 }
 
 func (o *WebSocketRequest) ToJson() string {