Bootstrap copied BFF and local accounts with public Sendico contracts (#34)

backend/pkg/db/repository/builder/accumulator.go

@@ -0,0 +1,11 @@
+package builder
+
+import "go.mongodb.org/mongo-driver/v2/bson"
+
+type Accumulator interface {
+	Build() bson.D
+}
+
+type GroupAccumulator interface {
+	Build() bson.D
+}