Applies perfsprint linter (#24999)

Replacing usages of fmt.Sprint with faster alternatives

Signed-off-by: Philippe Antoine <contact@catenacyber.fr>

server/channels/app/notification_email.go

@@ -9,6 +9,7 @@ import (
 	"html"
 	"html/template"
 	"io"
+	"strconv"
 	"strings"
 	"time"
 
@@ -343,9 +344,9 @@ func getFormattedPostTime(user *model.User, post *model.Post, useMilitaryTime bo
 
 	return formattedPostTime{
 		Time:     localTime,
-		Year:     fmt.Sprintf("%d", localTime.Year()),
+		Year:     strconv.Itoa(localTime.Year()),
 		Month:    translateFunc(localTime.Month().String()),
-		Day:      fmt.Sprintf("%d", localTime.Day()),
+		Day:      strconv.Itoa(localTime.Day()),
 		Hour:     hour,
 		Minute:   fmt.Sprintf("%02d"+period, localTime.Minute()),
 		TimeZone: zone,

server/channels/app/platform/session.go

@@ -5,6 +5,7 @@ package platform
 
 import (
 	"fmt"
+	"strconv"
 	"time"
 
 	"github.com/mattermost/mattermost/server/public/model"
@@ -229,7 +230,7 @@ func (ps *PlatformService) UpdateSessionsIsGuest(c request.CTX, userID string, i
 	}
 
 	for _, session := range sessions {
-		session.AddProp(model.SessionPropIsGuest, fmt.Sprintf("%t", isGuest))
+		session.AddProp(model.SessionPropIsGuest, strconv.FormatBool(isGuest))
 		err := ps.Store.Session().UpdateProps(session)
 		if err != nil {
 			mlog.Warn("Unable to update isGuest session", mlog.Err(err))