feat: Custom message files (#1992)

* feat: add get custom message text to admin api

* feat: read custom message texts from files

* feat: get languages in apis

* feat: get languages in apis

* feat: get languages in apis

* feat: pr feedback

* feat: docs

* feat: merge main

internal/auth/repository/eventsourcing/eventstore/iam.go

@@ -2,15 +2,35 @@ package eventstore
 
 import (
 	"context"
+	"net/http"
+
+	"github.com/caos/logging"
+	"golang.org/x/text/language"
+
+	"github.com/caos/zitadel/internal/i18n"
 	"github.com/caos/zitadel/internal/query"
 
 	"github.com/caos/zitadel/internal/iam/model"
 )
 
 type IAMRepository struct {
-	IAMID string
+	IAMID    string
+	LoginDir http.FileSystem
 
 	IAMV2QuerySide *query.Queries
+	supportedLangs []language.Tag
+}
+
+func (repo *IAMRepository) Languages(ctx context.Context) ([]language.Tag, error) {
+	if len(repo.supportedLangs) == 0 {
+		langs, err := i18n.SupportedLanguages(repo.LoginDir)
+		if err != nil {
+			logging.Log("ADMIN-tiMWs").WithError(err).Debug("unable to parse language")
+			return nil, err
+		}
+		repo.supportedLangs = langs
+	}
+	return repo.supportedLangs, nil
 }
 
 func (repo *IAMRepository) GetIAM(ctx context.Context) (*model.IAM, error) {