pipeline: outputs: azure_blob: add log_key to outputs

Signed-off-by: Thomas Wilk <[email protected]>

pipeline/outputs/azure_blob.md

@@ -26,6 +26,7 @@ We expose different configuration properties. The following table lists all the
 | sas\_token | Specify the Azure Storage shared access signatures to authenticate against the service. This configuration property is mandatory when `auth_type` is `sas`. |  |
 | container\_name | Name of the container that will contain the blobs. This configuration property is mandatory |  |
 | blob\_type | Specify the desired blob type. Fluent Bit supports `appendblob` and `blockblob`. | appendblob |
+| log\_key | By default, the entire log record is sent to blob storage. If you specify a key name with this option, only the value of that key is sent. |  |
 | auto\_create\_container | If `container_name` does not exist in the remote service, enabling this option will handle the exception and auto-create the container. | on |
 | path | Optional path to store your blobs. If your blob name is `myblob`, you can specify sub-directories where to store it using path, so setting path to `/logs/kubernetes` will store your blob in `/logs/kubernetes/myblob`. |  |
 | emulator\_mode | If you want to send data to an Azure emulator service like [Azurite](https://github.com/Azure/Azurite), enable this option so the plugin will format the requests to the expected format. | off |