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/admin/repository/eventsourcing/handler/mail_template.go

@@ -0,0 +1,105 @@
+package handler
+
+import (
+	"github.com/caos/logging"
+
+	"github.com/caos/zitadel/internal/eventstore"
+	"github.com/caos/zitadel/internal/eventstore/models"
+	es_models "github.com/caos/zitadel/internal/eventstore/models"
+	"github.com/caos/zitadel/internal/eventstore/query"
+	"github.com/caos/zitadel/internal/eventstore/spooler"
+	"github.com/caos/zitadel/internal/iam/repository/eventsourcing/model"
+	iam_es_model "github.com/caos/zitadel/internal/iam/repository/eventsourcing/model"
+	iam_model "github.com/caos/zitadel/internal/iam/repository/view/model"
+)
+
+type MailTemplate struct {
+	handler
+	subscription *eventstore.Subscription
+}
+
+func newMailTemplate(handler handler) *MailTemplate {
+	h := &MailTemplate{
+		handler: handler,
+	}
+
+	h.subscribe()
+
+	return h
+}
+
+func (m *MailTemplate) subscribe() {
+	m.subscription = m.es.Subscribe(m.AggregateTypes()...)
+	go func() {
+		for event := range m.subscription.Events {
+			query.ReduceEvent(m, event)
+		}
+	}()
+}
+
+const (
+	mailTemplateTable = "adminapi.mail_templates"
+)
+
+func (m *MailTemplate) ViewModel() string {
+	return mailTemplateTable
+}
+
+func (_ *MailTemplate) AggregateTypes() []es_models.AggregateType {
+	return []es_models.AggregateType{iam_es_model.IAMAggregate}
+}
+
+func (p *MailTemplate) CurrentSequence(event *models.Event) (uint64, error) {
+	sequence, err := p.view.GetLatestMailTemplateSequence(string(event.AggregateType))
+	if err != nil {
+		return 0, err
+	}
+	return sequence.CurrentSequence, nil
+}
+
+func (m *MailTemplate) EventQuery() (*models.SearchQuery, error) {
+	sequence, err := m.view.GetLatestMailTemplateSequence("")
+	if err != nil {
+		return nil, err
+	}
+	return es_models.NewSearchQuery().
+		AggregateTypeFilter(m.AggregateTypes()...).
+		LatestSequenceFilter(sequence.CurrentSequence), nil
+}
+
+func (m *MailTemplate) Reduce(event *models.Event) (err error) {
+	switch event.AggregateType {
+	case model.IAMAggregate:
+		err = m.processMailTemplate(event)
+	}
+	return err
+}
+
+func (m *MailTemplate) processMailTemplate(event *models.Event) (err error) {
+	template := new(iam_model.MailTemplateView)
+	switch event.Type {
+	case model.MailTemplateAdded:
+		err = template.AppendEvent(event)
+	case model.MailTemplateChanged:
+		template, err = m.view.MailTemplateByAggregateID(event.AggregateID)
+		if err != nil {
+			return err
+		}
+		err = template.AppendEvent(event)
+	default:
+		return m.view.ProcessedMailTemplateSequence(event)
+	}
+	if err != nil {
+		return err
+	}
+	return m.view.PutMailTemplate(template, event)
+}
+
+func (m *MailTemplate) OnError(event *models.Event, err error) error {
+	logging.LogWithFields("SPOOL-Wj8sf", "id", event.AggregateID).WithError(err).Warn("something went wrong in label template handler")
+	return spooler.HandleError(event, err, m.view.GetLatestMailTemplateFailedEvent, m.view.ProcessedMailTemplateFailedEvent, m.view.ProcessedMailTemplateSequence, m.errorCountUntilSkip)
+}
+
+func (o *MailTemplate) OnSuccess() error {
+	return spooler.HandleSuccess(o.view.UpdateMailTemplateSpoolerRunTimestamp)
+}