Add collection subType for sharedfiles collection

lib/models/magic_metadata.dart

@@ -7,6 +7,7 @@ const visibilityHidden = 2;
 
 // Collection SubType Constants
 const subTypeDefaultHidden = 1;
+const subTypeSharedFilesCollection = 2;
 
 const magicKeyVisibility = 'visibility';
 // key for collection subType
@@ -76,6 +77,7 @@ class CollectionMagicMetadata {
 
   // null/0 value -> no subType
   // 1 -> DEFAULT_HIDDEN COLLECTION for files hidden individually
+  // 2 -> Collections created for sharing selected files
   int? subType;
 
   CollectionMagicMetadata({required this.visibility, this.subType});
@@ -88,6 +90,10 @@ class CollectionMagicMetadata {
     return result;
   }
 
+  bool isSharedLinkCollection() {
+    return subType != null && subType == subTypeSharedFilesCollection;
+  }
+
   factory CollectionMagicMetadata.fromEncodedJson(String encodedJson) =>
       CollectionMagicMetadata.fromJson(jsonDecode(encodedJson));