feat(OIDC): add back channel logout (#8837)

# Which Problems Are Solved

Currently ZITADEL supports RP-initiated logout for clients. Back-channel
logout ensures that user sessions are terminated across all connected
applications, even if the user closes their browser or loses
connectivity providing a more secure alternative for certain use cases.

# How the Problems Are Solved

If the feature is activated and the client used for the authentication
has a back_channel_logout_uri configured, a
`session_logout.back_channel` will be registered. Once a user terminates
their session, a (notification) handler will send a SET (form POST) to
the registered uri containing a logout_token (with the user's ID and
session ID).

- A new feature "back_channel_logout" is added on system and instance
level
- A `back_channel_logout_uri` can be managed on OIDC applications
- Added a `session_logout` aggregate to register and inform about sent
`back_channel` notifications
- Added a `SecurityEventToken` channel and `Form`message type in the
notification handlers
- Added `TriggeredAtOrigin` fields to `HumanSignedOut` and
`TerminateSession` events for notification handling
- Exported various functions and types in the `oidc` package to be able
to reuse for token signing in the back_channel notifier.
- To prevent that current existing session termination events will be
handled, a setup step is added to set the `current_states` for the
`projections.notifications_back_channel_logout` to the current position

- [x] requires https://github.com/zitadel/oidc/pull/671

# Additional Changes

- Updated all OTEL dependencies to v1.29.0, since OIDC already updated
some of them to that version.
- Single Session Termination feature is correctly checked (fixed feature
mapping)

# Additional Context

- closes https://github.com/zitadel/zitadel/issues/8467
- TODO:
  - Documentation
  - UI to be done: https://github.com/zitadel/zitadel/issues/8469

---------

Co-authored-by: Hidde Wieringa <hidde@hiddewieringa.nl>

internal/command/logout_session.go

@@ -0,0 +1,24 @@
+package command
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/internal/repository/sessionlogout"
+	"github.com/zitadel/zitadel/internal/telemetry/tracing"
+)
+
+func (c *Commands) BackChannelLogoutSent(ctx context.Context, id, oidcSessionID, instanceID string) (err error) {
+	ctx, span := tracing.NewSpan(ctx)
+	defer func() { span.EndWithError(err) }()
+
+	sessionWriteModel := NewSessionLogoutWriteModel(id, instanceID, oidcSessionID)
+	if err = c.eventstore.FilterToQueryReducer(ctx, sessionWriteModel); err != nil {
+		return err
+	}
+
+	return c.pushAppendAndReduce(
+		ctx,
+		sessionWriteModel,
+		sessionlogout.NewBackChannelLogoutSentEvent(ctx, sessionWriteModel.aggregate, oidcSessionID),
+	)
+}