feat: add saml request to link to sessions (#9001)

# Which Problems Are Solved

It is currently not possible to use SAML with the Session API.

# How the Problems Are Solved

Add SAML service, to get and resolve SAML requests.
Add SAML session and SAML request aggregate, which can be linked to the
Session to get back a SAMLResponse from the API directly.

# Additional Changes

Update of dependency zitadel/saml to provide all functionality for
handling of SAML requests and responses.

# Additional Context

Closes #6053

---------

Co-authored-by: Livio Spring <livio.a@gmail.com>

internal/command/saml_request_model.go

@@ -0,0 +1,88 @@
+package command
+
+import (
+	"context"
+	"time"
+
+	"github.com/zitadel/zitadel/internal/api/authz"
+	"github.com/zitadel/zitadel/internal/domain"
+	"github.com/zitadel/zitadel/internal/eventstore"
+	"github.com/zitadel/zitadel/internal/repository/samlrequest"
+	"github.com/zitadel/zitadel/internal/zerrors"
+)
+
+type SAMLRequestWriteModel struct {
+	eventstore.WriteModel
+	aggregate *eventstore.Aggregate
+
+	LoginClient   string
+	ApplicationID string
+	ACSURL        string
+	RelayState    string
+	RequestID     string
+	Binding       string
+	Issuer        string
+	Destination   string
+
+	SessionID        string
+	UserID           string
+	AuthTime         time.Time
+	AuthMethods      []domain.UserAuthMethodType
+	SAMLRequestState domain.SAMLRequestState
+}
+
+func NewSAMLRequestWriteModel(ctx context.Context, id string) *SAMLRequestWriteModel {
+	return &SAMLRequestWriteModel{
+		WriteModel: eventstore.WriteModel{
+			AggregateID: id,
+		},
+		aggregate: &samlrequest.NewAggregate(id, authz.GetInstance(ctx).InstanceID()).Aggregate,
+	}
+}
+
+func (m *SAMLRequestWriteModel) Reduce() error {
+	for _, event := range m.Events {
+		switch e := event.(type) {
+		case *samlrequest.AddedEvent:
+			m.LoginClient = e.LoginClient
+			m.ApplicationID = e.ApplicationID
+			m.ACSURL = e.ACSURL
+			m.RelayState = e.RelayState
+			m.RequestID = e.RequestID
+			m.Binding = e.Binding
+			m.Issuer = e.Issuer
+			m.Destination = e.Destination
+			m.SAMLRequestState = domain.SAMLRequestStateAdded
+		case *samlrequest.SessionLinkedEvent:
+			m.SessionID = e.SessionID
+			m.UserID = e.UserID
+			m.AuthTime = e.AuthTime
+			m.AuthMethods = e.AuthMethods
+		case *samlrequest.FailedEvent:
+			m.SAMLRequestState = domain.SAMLRequestStateFailed
+		case *samlrequest.SucceededEvent:
+			m.SAMLRequestState = domain.SAMLRequestStateSucceeded
+		}
+	}
+	return m.WriteModel.Reduce()
+}
+
+func (m *SAMLRequestWriteModel) Query() *eventstore.SearchQueryBuilder {
+	return eventstore.NewSearchQueryBuilder(eventstore.ColumnsEvent).
+		AddQuery().
+		AggregateTypes(samlrequest.AggregateType).
+		AggregateIDs(m.AggregateID).
+		Builder()
+}
+
+// CheckAuthenticated checks that the auth request exists, a session must have been linked
+func (m *SAMLRequestWriteModel) CheckAuthenticated() error {
+	if m.SessionID == "" {
+		return zerrors.ThrowPreconditionFailed(nil, "AUTHR-3dNRNwSYeC", "Errors.SAMLRequest.NotAuthenticated")
+	}
+	// check that the requests exists, but has not succeeded yet
+	if m.SAMLRequestState == domain.SAMLRequestStateAdded {
+		return nil
+	}
+	return zerrors.ThrowPreconditionFailed(nil, "AUTHR-krQV50AlnJ", "Errors.SAMLRequest.NotAuthenticated")
+}