Continued scaffolding and interface definitions

services/data_service/internal/node/source/source.go

@@ -1,2 +1,20 @@
 // Package source
 package source
+
+import (
+	"context"
+
+	"gitlab.michelsen.id/phillmichelsen/tessera/services/data_service/internal/node"
+)
+
+type Source interface {
+	Start(ctx context.Context, cfg string, io IO) error
+	Stop()
+
+	Serve(key string) error
+	Unserve(key string) error
+}
+
+type IO interface {
+	node.Sender
+}