This adds a new configuration setting: AzurePublishEndpoints, similar
to the existing S3PublishEndpoints and SwiftPublishEndpoints.
For each endpoint, the following has to be defined:
- accountName
- accountKey
- container
- prefix
Azure tests require the following environment variables to be set:
- AZURE_STORAGE_ACCOUNT
- AZURE_STORAGE_ACCESS_KEY
With either of these not set, Azure-specific tests are skipped.
