V15: Implement sorting for the in-memory navigation structures (document and media)

[elit0451]

Details

• The NavigationNode model now keeps track of the sortOrder as well;
  • Parent and Children properties are refactored to reference Guid keys instead of the whole NavigationNode object - which means we need to resolve the NavigationNode from the key in all the properties' usages (i.e. ContentNavigationServiceBase).
• Adding a new UpdateSortOrder() to the INavigationManagementService.cs;
  • Add() changed its signature to have a sortOrder parameter as well, due to a special case when adding nodes directly to the root (where parentKey is null), the sort order must be provided to ensure the item appears in the correct position among other root-level items. We can't calculate the amount of children based on the parent here.
• Cache refreshers (document and media) are updated to update the sort order in the navigation structure;
• Added integration and unit tests for both document and media.

Test

• Create a simple content type with template;
• Create a nested tree structure that you would use for sorting, something like:

Root
   - Child 1
     - Grandchild 1
     - Grandchild 2
   - Child 2
     - Grandchild 3
       - Great-grandchild 1
   - Child 3
     - Grandchild 4

• Create a new Partial View from "List Descendants From Current Page" and call it ListDescendants.cshtml;
• In the Root template use the following line @await Html.PartialAsync("ListDescendants") to display it, so the template looks like:

@using Umbraco.Cms.Web.Common.PublishedModels;
@inherits Umbraco.Cms.Web.Common.Views.UmbracoViewPage
@{
	Layout = null;
}

<h2>Descendants</h2>
@await Html.PartialAsync("ListDescendants")

• In the Content section, sort the children on a parent node;
• Verify that the tree from the template reflects those changes.

[bergmania]

Looks good and tests out great. I love all the new tests 💪