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_view.go

@@ -0,0 +1,60 @@
+package model
+
+import (
+	"time"
+
+	"github.com/caos/zitadel/internal/model"
+)
+
+type MailTextsView struct {
+	Texts   []*MailTextView
+	Default bool
+}
+type MailTextView struct {
+	AggregateID  string
+	MailTextType string
+	Language     string
+	Title        string
+	PreHeader    string
+	Subject      string
+	Greeting     string
+	Text         string
+	ButtonText   string
+	Default      bool
+
+	CreationDate time.Time
+	ChangeDate   time.Time
+	Sequence     uint64
+}
+
+type MailTextSearchRequest struct {
+	Offset        uint64
+	Limit         uint64
+	SortingColumn MailTextSearchKey
+	Asc           bool
+	Queries       []*MailTextSearchQuery
+}
+
+type MailTextSearchKey int32
+
+const (
+	MailTextSearchKeyUnspecified MailTextSearchKey = iota
+	MailTextSearchKeyAggregateID
+	MailTextSearchKeyMailTextType
+	MailTextSearchKeyLanguage
+)
+
+type MailTextSearchQuery struct {
+	Key    MailTextSearchKey
+	Method model.SearchMethod
+	Value  interface{}
+}
+
+type MailTextSearchResponse struct {
+	Offset      uint64
+	Limit       uint64
+	TotalResult uint64
+	Result      []*MailTextView
+	Sequence    uint64
+	Timestamp   time.Time
+}