Feature/reorder spaces api integration (#362)

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## Description

Integrated reordering spaces with the API.
Fixed drop target bug, where the canvas wouldn't show the first drop
target in the tree.

## Type of Change

<!--- Put an `x` in all the boxes that apply: -->

- [ x ] ✨ New feature (non-breaking change which adds functionality)
- [ x ] 🛠️ Bug fix (non-breaking change which fixes an issue)
- [ ] ❌ Breaking change (fix or feature that would cause existing
functionality to change)
- [   ] 🧹 Code refactor
- [   ] ✅ Build configuration change
- [   ] 📝 Documentation
- [   ] 🗑️ Chore

lib/utils/constants/api_const.dart

@@ -41,6 +41,8 @@ abstract class ApiEndpoints {
       '/projects/{projectId}/communities/{communityId}/spaces/{spaceId}';
   static const String getSpaceHierarchy =
       '/projects/{projectId}/communities/{communityId}/spaces';
+  static const String reorderSpaces =
+      '/projects/{projectUuid}/communities/{communityUuid}/spaces/{parentSpaceUuid}/spaces/order';
 
 // Community Module
   static const String createCommunity = '/projects/{projectId}/communities';