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/iam/model/mail_text.go

@@ -0,0 +1,28 @@
+package model
+
+import (
+	"github.com/caos/zitadel/internal/eventstore/models"
+)
+
+type MailTexts struct {
+	Texts   []*MailText
+	Default bool
+}
+type MailText struct {
+	models.ObjectRoot
+
+	State        PolicyState
+	Default      bool
+	MailTextType string
+	Language     string
+	Title        string
+	PreHeader    string
+	Subject      string
+	Greeting     string
+	Text         string
+	ButtonText   string
+}
+
+func (p *MailText) IsValid() bool {
+	return p.ObjectRoot.AggregateID != ""
+}