feat: e-mail templates (#1158)

* View definition added

* Get templates and texts from the database.

* Fill in texts in templates

* Fill in texts in templates

* Client API added

* Weekly backup

* Weekly backup

* Daily backup

* Weekly backup

* Tests added

* Corrections from merge branch

* Fixes from pull request review

internal/api/grpc/admin/text.go

@@ -0,0 +1,32 @@
+package admin
+
+import (
+	"context"
+
+	"github.com/caos/zitadel/pkg/grpc/admin"
+	"github.com/golang/protobuf/ptypes/empty"
+)
+
+func (s *Server) GetDefaultMailTexts(ctx context.Context, _ *empty.Empty) (*admin.DefaultMailTextsView, error) {
+	result, err := s.iam.GetDefaultMailTexts(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return textsViewFromModel(result), nil
+}
+
+func (s *Server) GetDefaultMailText(ctx context.Context, textType string, language string) (*admin.DefaultMailTextView, error) {
+	result, err := s.iam.GetDefaultMailText(ctx, textType, language)
+	if err != nil {
+		return nil, err
+	}
+	return textViewFromModel(result), nil
+}
+
+func (s *Server) UpdateDefaultMailText(ctx context.Context, text *admin.DefaultMailTextUpdate) (*admin.DefaultMailText, error) {
+	result, err := s.iam.ChangeDefaultMailText(ctx, textToModel(text))
+	if err != nil {
+		return nil, err
+	}
+	return textFromModel(result), nil
+}