Improve documentation for AzureBaseHook DefaultAzureCredential support (

#34097)

* docs(providers/microsoft): improve documentation for AzureBaseHook DefaultAzureCredential support

* docs(providers/microsoft): add link to where DefaultAzureCredential is mentioned

* docs(providers/microsoft): extract links to doc end

docs/apache-airflow-providers-microsoft-azure/connections/azure.rst

@@ -27,17 +27,16 @@ The Microsoft Azure connection type enables the Azure Integrations.
 Authenticating to Azure
 -----------------------
 
-There are three ways to connect to Azure using Airflow.
+There are four ways to connect to Azure using Airflow.
 
-1. Use `token credentials
-   <https://docs.microsoft.com/en-us/azure/developer/python/azure-sdk-authenticate?tabs=cmd#authenticate-with-token-credentials>`_
+1. Use `token credentials`_
    i.e. add specific credentials (client_id, secret, tenant) and subscription id to the Airflow connection.
-2. Use a `JSON file
-   <https://docs.microsoft.com/en-us/azure/developer/python/azure-sdk-authenticate?tabs=cmd#authenticate-with-a-json-file>`_
-   i.e. create a key file on disk and link to it in the Airflow connection.
-3. Use a `JSON dictionary
-   <https://docs.microsoft.com/en-us/azure/developer/python/azure-sdk-authenticate?tabs=cmd#authenticate-with-a-json-dictionary>`_
+2. Use a `JSON file`_
+3. Use a `JSON dictionary`_
    i.e. add a key config directly into the Airflow connection.
+4. Fallback on `DefaultAzureCredential`_.
+   This includes a mechanism to try different options to authenticate: Managed System Identity, environment variables, authentication through Azure CLI and etc.
+   ``subscriptionId`` is required in this authentication mechanism.
 
 Only one authorization method can be used at a time. If you need to manage multiple credentials or keys then you should
 configure multiple connections.
@@ -53,10 +52,12 @@ Configuring the Connection
 Login (optional)
     Specify the ``client_id`` used for the initial connection.
     This is only needed for *token credentials* authentication mechanism.
+    It can be left out to fall back on DefaultAzureCredential_.
 
 Password (optional)
     Specify the ``secret`` used for the initial connection.
     This is only needed for *token credentials* authentication mechanism.
+    It can be left out to fall back on DefaultAzureCredential_.
 
 Extra (optional)
     Specify the extra parameters (as json dictionary) that can be used in Azure connection.
@@ -65,12 +66,14 @@ Extra (optional)
     * ``tenantId``: Specify the tenant to use.
       This is only needed for *token credentials* authentication mechanism.
     * ``subscriptionId``: Specify the subscription id to use.
-      This is only needed for *token credentials* authentication mechanism.
+      This is only needed for *token credentials* and DefaultAzureCredential_ authentication mechanism.
     * ``key_path``: If set, it uses the *JSON file* authentication mechanism.
       It specifies the path to the json file that contains the authentication information.
     * ``key_json``: If set, it uses the *JSON dictionary* authentication mechanism.
       It specifies the json that contains the authentication information.
 
+    The entire extra column can be left out to fall back on DefaultAzureCredential_.
+
 When specifying the connection in environment variable you should specify
 it using URI syntax.
 
@@ -81,3 +84,9 @@ For example:
 .. code-block:: bash
 
    export AIRFLOW_CONN_AZURE_DEFAULT='azure://?key_path=%2Fkeys%2Fkey.json'
+
+
+.. _token credentials: https://docs.microsoft.com/en-us/azure/developer/python/azure-sdk-authenticate?tabs=cmd#authenticate-with-token-credentials
+.. _JSON file: https://docs.microsoft.com/en-us/azure/developer/python/azure-sdk-authenticate?tabs=cmd#authenticate-with-a-json-file
+.. _JSON dictionary: https://docs.microsoft.com/en-us/azure/developer/python/azure-sdk-authenticate?tabs=cmd#authenticate-with-a-json-dictionary>
+.. _DefaultAzureCredential: https://docs.microsoft.com/en-us/python/api/overview/azure/identity-readme?view=azure-python#defaultazurecredential