Add reference slot clone helper

internal/framework/contracts/contracts.go

@@ -132,6 +132,18 @@ type ReferenceSlot struct {
 	MaxBytes           int64    `json:"max_bytes,omitempty"`
 }
 
+func CloneReferenceSlots(slots []ReferenceSlot) []ReferenceSlot {
+	if len(slots) == 0 {
+		return nil
+	}
+	out := make([]ReferenceSlot, len(slots))
+	for i, slot := range slots {
+		slot.AcceptedMediaTypes = append([]string(nil), slot.AcceptedMediaTypes...)
+		out[i] = slot
+	}
+	return out
+}
+
 type ReferenceOrigin struct {
 	Type string `json:"type"`
 	URI  string `json:"uri,omitempty"`

internal/framework/contracts/contracts_test.go

@@ -3,6 +3,7 @@ package contracts
 import (
 	"context"
 	"encoding/json"
+	"reflect"
 	"testing"
 
 	"gitea.maximumdirect.net/eric/notarius/internal/core/artifacts"
@@ -225,6 +226,59 @@ func TestReferenceSetDataTypes(t *testing.T) {
 	}
 }
 
+func TestCloneReferenceSlotsEmptyInputReturnsNil(t *testing.T) {
+	if got := CloneReferenceSlots(nil); got != nil {
+		t.Fatalf("CloneReferenceSlots(nil) = %#v, want nil", got)
+	}
+	if got := CloneReferenceSlots([]ReferenceSlot{}); got != nil {
+		t.Fatalf("CloneReferenceSlots(empty) = %#v, want nil", got)
+	}
+}
+
+func TestCloneReferenceSlotsPreservesFields(t *testing.T) {
+	slots := []ReferenceSlot{
+		{
+			Name:               "roster",
+			Description:        "Known characters",
+			Required:           true,
+			AcceptedMediaTypes: []string{"text/plain", "text/markdown"},
+			Multiple:           true,
+			MaxBytes:           4096,
+		},
+		{
+			Name:        "glossary",
+			Description: "Campaign terms",
+			MaxBytes:    2048,
+		},
+	}
+
+	got := CloneReferenceSlots(slots)
+
+	if !reflect.DeepEqual(got, slots) {
+		t.Fatalf("CloneReferenceSlots() = %#v, want %#v", got, slots)
+	}
+}
+
+func TestCloneReferenceSlotsCopiesAcceptedMediaTypes(t *testing.T) {
+	slots := []ReferenceSlot{
+		{
+			Name:               "party",
+			AcceptedMediaTypes: []string{"application/json", "text/plain"},
+		},
+	}
+
+	got := CloneReferenceSlots(slots)
+	got[0].Name = "changed"
+	got[0].AcceptedMediaTypes[0] = "text/markdown"
+
+	if slots[0].Name != "party" {
+		t.Fatalf("source slot name = %q, want unchanged", slots[0].Name)
+	}
+	if slots[0].AcceptedMediaTypes[0] != "application/json" {
+		t.Fatalf("source AcceptedMediaTypes aliased clone: %#v", slots[0].AcceptedMediaTypes)
+	}
+}
+
 func TestReferenceItemJSONOmitsContent(t *testing.T) {
 	item := ReferenceItem{
 		SlotName:  "roster",