update AzureBaseHook to return credentials that supports get_token method

[karunpoudel]

Databases like Snowflake and Azure Postgres Flex support connection using Azure OAUTH token. Newer Azure Identity credential objects like ClientSecretCredential and DefaultAzureCredential support get_token method which can be used to generate OAUTH token. SnowflakeHook and PostgresHook can leverage AzureBaseHook to retrieve required token.

In this PR:

• Expose the credential object directly using get_credential method and make sdk_client argument optional so that the credential object can be retrieved without needing sdk_client. eg. AzureBaseHook().get_credential()
• Added new extra use_azure_identity_object in connection for backward compatibility. When set to true, get_credential method will return newer credential object of type ClientSecretCredential or DefaultAzureCredential instead of current ServicePrincipalCredentials or AzureIdentityCredentialAdapter. Current credential object doesn't support get_token method. eg. AzureBaseHook().get_credential().get_token()

I am ok with not making sdk_client argument optional if there is any concern.

Usage:

Create base azure connection using either client_secret or default azure credential.

# Using client_secret
AIRFLOW_CONN_AZURE_SP=azure://client_id:client_secret@/?tenantId=xyz&use_azure_identity_object=true

# Using default azure credentials
AIRFLOW_CONN_AZURE_SP=azure:///?use_azure_identity_object=true

Use above connection to retrieve token to connect to specific resource (e.g., azure postgres flex server).

from airflow.models import Connection
conn = Connection.get_connection_from_secrets("azure_sp")
azure_base_hook= conn.get_hook()
scope = "https://ossrdbms-aad.database.windows.net/.default"
password = azure_base_hook.get_token(scope).token

PostgresHook could be updated to retrieve token using azure connection similar to how it currently uses aws connection.

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[karunpoudel]

Hi, could someone look into this, please?

[karunpoudel-chr]

@potiuk , can this be assigned to anyone for review?

[potiuk]

Please avoid pinging people directly - unless you know they are interested - and no, I am not assigning reviewers - and also here thi is work on voluntary bases and your PR might get picked by someone. If it is not and it is ready to be reviewed, you can just ping in general in your PR or in slack, but you should not expect that pinging random individuals is a good idea.

And ideally - this generic pinging should happen after the Pr gets green and is related on top of latest main. Which i think has not happened yet for the PR?