Digital Assets: Azure folders are slow to open

[mikebigun]

fixes #2697

After some investigation we found it loads Azure content using very small batches of data in a loop. On every Azure folder click, system synchronizes content and makes huge amount of iterations to upload all files. See:

Dnn.Platform/DNN Platform/Providers/FolderProviders/AzureFolderProvider/AzureFolderProvider.cs

Line 159 in 9968677

resultSegment = container.ListBlobsSegmented("", true, BlobListingDetails.All, 10, continuationToken, null, null);

To improve performance, I added SyncBatchSize setting which is now available on UI. It is possible to configure size of batches to load from Azure in one call. Customer can make it configured to their needs, smaller values means we will need more round trips to fetch all files, large numbers will potentially lead to timeouts in case of big repositories, but at same time will improve performance for a small repos.

Below you'll find few changes:

1. SyncBatchSise setting is added to UI. It gets saved in database and used to load certain number of files from Azure during one call.
2. I did a small refactoring for the constants. I moved constant strings to one file and used it in a few places within one project.

[mitchelsellers]

Great change, appreciate the extra work to extract the constants as well!

[daguiler]

Good job! I just added a few minor suggestions.

[donker]

Good for me