Add relative destinations to import declarations

internal/engine/directives.go

@@ -91,6 +91,27 @@ func parseImportDeclaration(node *document.Node, declarationPath Path) (importDe
 				return importDeclaration{}, []Diagnostic{nodeImportDiagnostic(CodeImportInvalid, fieldPath, "optional must be a boolean", entry.Value)}
 			}
 			declaration.optional = entry.Value.Text == "true"
+		case "destination":
+			if entry.Value.Kind != document.Sequence {
+				return importDeclaration{}, []Diagnostic{nodeImportDiagnostic(CodeImportInvalid, fieldPath, "destination must be a sequence of strings", entry.Value)}
+			}
+			relative := Path{segments: make([]pathSegment, 0, len(entry.Value.Sequence))}
+			for index, item := range entry.Value.Sequence {
+				memberPath := fieldPath.Index(index)
+				if item.Kind != document.String {
+					return importDeclaration{}, []Diagnostic{nodeImportDiagnostic(CodeImportInvalid, memberPath, "destination members must be strings", item)}
+				}
+				member := Path{segments: []pathSegment{{kind: pathSegmentKey, key: item.Text}}}
+				if _, err := normalizeDestination(member); err != nil {
+					return importDeclaration{}, []Diagnostic{nodeImportDiagnostic(CodeImportInvalid, memberPath, "destination members must be non-reserved mapping keys", item)}
+				}
+				relative.segments = append(relative.segments, pathSegment{kind: pathSegmentKey, key: item.Text})
+			}
+			normalized, err := normalizeDestination(relative)
+			if err != nil {
+				return importDeclaration{}, []Diagnostic{nodeImportDiagnostic(CodeImportInvalid, fieldPath, "destination must contain only non-reserved mapping keys", entry.Value)}
+			}
+			declaration.destination = normalized
 		default:
 			return importDeclaration{}, []Diagnostic{nodeImportDiagnostic(CodeImportInvalid, fieldPath, "import declaration field is not recognized", entry.Value)}
 		}