Document the Azure BLOB storage integration.

Resolve #4299

docs/en/Blob-Storing-Azure.md

@@ -1,3 +1,69 @@
 # BLOB Storing Azure Provider
 
-This feature will be available with v3.0!
+BLOB Storing Azure Provider can store BLOBs in [Azure Blob storage](https://azure.microsoft.com/en-us/services/storage/blobs/).
+
+> Read the [BLOB Storing document](Blob-Storing.md) to understand how to use the BLOB storing system. This document only covers how to configure containers to use a database as the storage provider.
+
+## Installation
+
+You can use dotnet cli to install [the package](https://www.nuget.org/packages/Volo.Abp.BlobStoring.Azure).
+
+````bash
+dotnet add package Volo.Abp.BlobStoring.Azure
+````
+
+After installation, add `DepenedsOn` attribute of the `AbpBlobStoringAzureModule` module   to your [module](Module-Development-Basics.md).
+
+Whenever you add a NuGet package to a project, also add the module class dependency.
+
+### Configuring the Containers
+
+Configuration is done in the `ConfigureServices` method of your [module](Module-Development-Basics.md) class, as explained in the [BLOB Storing document](Blob-Storing.md).
+
+**Example: Configure to use the azure storage provider by default**
+
+````csharp
+Configure<AbpBlobStoringOptions>(options =>
+{
+    options.Containerscontainer.UseAzure(azure =>
+    {
+        azure.ConnectionString = "your azure connection string";
+        azure.ContainerName = "your azure container name";
+        azure.CreateContainerIfNotExists = false;
+    });
+});
+````
+
+> See the [BLOB Storing document](Blob-Storing.md) to learn how to configure this provider for a specific container.
+
+## Options
+
+* **ConnectionString** (string): A connection string includes the authorization information required for your application to access data in an Azure Storage account at runtime using Shared Key authorization. Please refer to Azure documentation: https://docs.microsoft.com/en-us/azure/storage/common/storage-configure-connection-string
+
+* **ContainerName** (string): You can specify the container name in azure. If it is not specified, the `ContainerName` of the `BlobProviderArgs` will be used. However, please note that Azure has some rules for naming containers. A container name must be a valid DNS name, conforming to the [following naming rules](https://docs.microsoft.com/en-us/rest/api/storageservices/naming-and-referencing-containers--blobs--and-metadata#container-names).
+
+* Container-names rules:
+    - Container names must start or end with a letter or number, and can contain only letters, numbers, and the dash (-) character.
+    - Every dash (-) character must be immediately preceded and followed by a letter or number; consecutive dashes are not permitted in container names.
+    - All letters in a container name must be lowercase.
+    - Container names must be from 3 through 63 characters long.
+
+* **CreateContainerIfNotExists** (bool): Default value is `false`, If a container does not exist in azure, `AzureBlobProvider` will try to create it. Please refer to the naming rules mentioned above.
+
+
+## Azure Blob Name Calculator
+
+Azure Blob Provider organizes BLOB name and implements some conventions. The full name of a BLOB is determined by the following rules by default:
+
+* Appends `host` string if [current tenant](Multi-Tenancy.md) is `null` (or multi-tenancy is disabled for the container - see the [BLOB Storing document](Blob-Storing.md) to learn how to disable multi-tenancy for a container).
+* Appends `tenants/<tenant-id>` string if current tenant is not `null`.
+
+```csharp
+var blobName = CurrentTenant.Id == null
+              ? $"host/{args.BlobName}"
+              : $"tenants/{CurrentTenant.Id.Value.ToString("D")}/{args.BlobName}";
+```
+
+### Other Services
+
+* `AzureBlobProvider` is the main service that implements the Azure BLOB storage provider, if you want to override/replace it via [dependency injection](Dependency-Injection.md) (don't replace `IBlobProvider` interface, but replace `AzureBlobProvider` class).