Cross-signing groundwork (#1953)

* Cross-signing groundwork

* Update to matrix-org/gomatrixserverlib#274

* Fix gobind builds, which stops unit tests in CI from yelling

* Some changes from review comments

* Fix build by passing in UIA

* Update to matrix-org/gomatrixserverlib@bec8d22

* Process master/self-signing keys from devices call

* nolint

* Enum-ify the key type in the database

* Process self-signing key too

* Fix sanity check in device list updater

* Fix check

* Fix sytest, hopefully

* Fix build

keyserver/consumers/eduserver.go

@@ -0,0 +1,61 @@
+package consumers
+
+import (
+	"fmt"
+
+	"github.com/matrix-org/dendrite/internal"
+	"github.com/matrix-org/dendrite/keyserver/api"
+	"github.com/matrix-org/dendrite/keyserver/storage"
+	"github.com/matrix-org/dendrite/setup/config"
+	"github.com/matrix-org/dendrite/setup/process"
+
+	"github.com/Shopify/sarama"
+)
+
+type OutputSigningKeyUpdateConsumer struct {
+	eduServerConsumer *internal.ContinualConsumer
+	keyDB             storage.Database
+	keyAPI            api.KeyInternalAPI
+	serverName        string
+}
+
+func NewOutputSigningKeyUpdateConsumer(
+	process *process.ProcessContext,
+	cfg *config.Dendrite,
+	kafkaConsumer sarama.Consumer,
+	keyDB storage.Database,
+	keyAPI api.KeyInternalAPI,
+) *OutputSigningKeyUpdateConsumer {
+	consumer := internal.ContinualConsumer{
+		Process:        process,
+		ComponentName:  "keyserver/eduserver",
+		Topic:          cfg.Global.Kafka.TopicFor(config.TopicOutputSigningKeyUpdate),
+		Consumer:       kafkaConsumer,
+		PartitionStore: keyDB,
+	}
+	s := &OutputSigningKeyUpdateConsumer{
+		eduServerConsumer: &consumer,
+		keyDB:             keyDB,
+		keyAPI:            keyAPI,
+		serverName:        string(cfg.Global.ServerName),
+	}
+	consumer.ProcessMessage = s.onMessage
+
+	return s
+}
+
+func (s *OutputSigningKeyUpdateConsumer) Start() error {
+	return s.eduServerConsumer.Start()
+}
+
+func (s *OutputSigningKeyUpdateConsumer) onMessage(msg *sarama.ConsumerMessage) error {
+	/*
+		var output eduapi.OutputSigningKeyUpdate
+		if err := json.Unmarshal(msg.Value, &output); err != nil {
+			log.WithError(err).Errorf("eduserver output log: message parse failure")
+			return nil
+		}
+		return nil
+	*/
+	return fmt.Errorf("TODO")
+}