add doc string for authority setting (Azure#23659)

* add doc string for authority setting

* updates

Author: xiangyan99

sdk/identity/azure-identity/azure/identity/_credentials/environment.py

@@ -38,12 +38,18 @@ class EnvironmentCredential(object):
       - **AZURE_TENANT_ID**: ID of the service principal's tenant. Also called its 'directory' ID.
       - **AZURE_CLIENT_ID**: the service principal's client ID
       - **AZURE_CLIENT_SECRET**: one of the service principal's client secrets
+      - **AZURE_AUTHORITY_HOST**: authority of an Azure Active Directory endpoint, for example
+        "login.microsoftonline.com", the authority for Azure Public Cloud, which is the default
+        when no value is given.
 
     Service principal with certificate:
       - **AZURE_TENANT_ID**: ID of the service principal's tenant. Also called its 'directory' ID.
       - **AZURE_CLIENT_ID**: the service principal's client ID
       - **AZURE_CLIENT_CERTIFICATE_PATH**: path to a PEM or PKCS12 certificate file including the private key. The
         certificate must not be password-protected.
+      - **AZURE_AUTHORITY_HOST**: authority of an Azure Active Directory endpoint, for example
+        "login.microsoftonline.com", the authority for Azure Public Cloud, which is the default
+        when no value is given.
 
     User with username and password:
       - **AZURE_CLIENT_ID**: the application's client ID
@@ -52,6 +58,9 @@ class EnvironmentCredential(object):
       - **AZURE_TENANT_ID**: (optional) ID of the service principal's tenant. Also called its 'directory' ID.
         If not provided, defaults to the 'organizations' tenant, which supports only Azure Active Directory work or
         school accounts.
+      - **AZURE_AUTHORITY_HOST**: authority of an Azure Active Directory endpoint, for example
+        "login.microsoftonline.com", the authority for Azure Public Cloud, which is the default
+        when no value is given.
     """
 
     def __init__(self, **kwargs):

sdk/identity/azure-identity/azure/identity/aio/_credentials/environment.py

@@ -31,12 +31,18 @@ class EnvironmentCredential(AsyncContextManager):
       - **AZURE_TENANT_ID**: ID of the service principal's tenant. Also called its 'directory' ID.
       - **AZURE_CLIENT_ID**: the service principal's client ID
       - **AZURE_CLIENT_SECRET**: one of the service principal's client secrets
+      - **AZURE_AUTHORITY_HOST**: authority of an Azure Active Directory endpoint, for example
+        "login.microsoftonline.com", the authority for Azure Public Cloud, which is the default
+        when no value is given.
 
     Service principal with certificate:
       - **AZURE_TENANT_ID**: ID of the service principal's tenant. Also called its 'directory' ID.
       - **AZURE_CLIENT_ID**: the service principal's client ID
       - **AZURE_CLIENT_CERTIFICATE_PATH**: path to a PEM or PKCS12 certificate file including the private key. The
         certificate must not be password-protected.
+      - **AZURE_AUTHORITY_HOST**: authority of an Azure Active Directory endpoint, for example
+        "login.microsoftonline.com", the authority for Azure Public Cloud, which is the default
+        when no value is given.
     """
 
     def __init__(self, **kwargs: "Any") -> None: