[GH-15906][MM-22844] Redesign message notification emails. (#17184)

* Redesign message notification emails.

* Fix tests and linter.

* Fix tests

* Fix tests

* gofmt.

* Fix date separator

* Update html files

* Remove date for message notification email.

* Modify subtitle for mentions and direct and group messages.

* Fix lint error

* Fix DM subtitle.

* Fixing translations

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>
Co-authored-by: Jesús Espino <jespinog@gmail.com>

app/server.go

@@ -4,12 +4,14 @@
 package app
 
 import (
+	"bytes"
 	"context"
 	"crypto/tls"
 	"encoding/json"
 	"fmt"
 	"hash/maphash"
 	"html/template"
+	"io"
 	"io/ioutil"
 	"net"
 	"net/http"
@@ -2114,6 +2116,76 @@ func (a *App) generateSupportPacketYaml() (*model.FileData, string) {
 	return nil, warning
 }
 
+func (s *Server) GetProfileImage(user *model.User) ([]byte, bool, *model.AppError) {
+	if *s.Config().FileSettings.DriverName == "" {
+		img, appErr := s.GetDefaultProfileImage(user)
+		if appErr != nil {
+			return nil, false, appErr
+		}
+		return img, false, nil
+	}
+
+	path := "users/" + user.Id + "/profile.png"
+
+	data, err := s.ReadFile(path)
+	if err != nil {
+		img, appErr := s.GetDefaultProfileImage(user)
+		if appErr != nil {
+			return nil, false, appErr
+		}
+
+		if user.LastPictureUpdate == 0 {
+			if _, err := s.WriteFile(bytes.NewReader(img), path); err != nil {
+				return nil, false, err
+			}
+		}
+		return img, true, nil
+	}
+
+	return data, false, nil
+}
+
+func (s *Server) GetDefaultProfileImage(user *model.User) ([]byte, *model.AppError) {
+	var img []byte
+	var appErr *model.AppError
+
+	if user.IsBot {
+		img = model.BotDefaultImage
+		appErr = nil
+	} else {
+		img, appErr = CreateProfileImage(user.Username, user.Id, *s.Config().FileSettings.InitialFont)
+	}
+	if appErr != nil {
+		return nil, appErr
+	}
+	return img, nil
+}
+
+func (s *Server) ReadFile(path string) ([]byte, *model.AppError) {
+	backend, err := s.FileBackend()
+	if err != nil {
+		return nil, err
+	}
+	result, nErr := backend.ReadFile(path)
+	if nErr != nil {
+		return nil, model.NewAppError("ReadFile", "api.file.read_file.app_error", nil, nErr.Error(), http.StatusInternalServerError)
+	}
+	return result, nil
+}
+
+func (s *Server) WriteFile(fr io.Reader, path string) (int64, *model.AppError) {
+	backend, err := s.FileBackend()
+	if err != nil {
+		return 0, err
+	}
+
+	result, nErr := backend.WriteFile(fr, path)
+	if nErr != nil {
+		return result, model.NewAppError("WriteFile", "api.file.write_file.app_error", nil, nErr.Error(), http.StatusInternalServerError)
+	}
+	return result, nil
+}
+
 func runDNDStatusExpireJob(a *App) {
 	if a.IsLeader() {
 		a.srv.dndnTaskMut.Lock()