Add LDAP Authentication Support to Teradata Provider

[sc250072]

This PR introduces a pluggable authentication framework to the Teradata provider, enabling support for multiple authentication mechanisms including native Teradata (TD2) and LDAP.

Changes

New Authentication Framework (providers/teradata/src/airflow/providers/teradata/auth/)

1. base.py: Abstract TeradataAuthMechanism base class
2. td2.py: Native Teradata (TD2) authentication (default)
3. ldap.py: New LDAP authentication support
4. registry.py: Mechanism registry for dynamic auth provider lookup

Enhanced Teradata Hook

1. Refactored _get_conn_config_teradatasql() to use authentication registry
2. New _add_shared_connection_params() for SSL/TLS and transaction mode config
3. Updated sqlalchemy_url property to carry logmech parameter

Documentation Updates

1. Added LDAP authentication configuration examples
2. Documented logmech parameter and connection URI format
3. Added Port field documentation

Bug Fix

1. teradata_to_teradata.py: Fixed cursor.execute() when sql_params is empty

Comprehensive Tests

1. Auth mechanism tests (TD2, LDAP, registry)
2. Hook integration tests with LDAP and logdata support

Configuration Example

LDAP Authentication:

JSON
{
"logmech": "LDAP",
"sslmode": "verify-ca",
"sslca": "/tmp/server-ca.pem"
}

Backward Compatibility

✅ Fully backward compatible - TD2 remains default when logmech is not specified.

Teradata Provider System Health Dashboard: https://teradata.github.io/airflow/

Teradata Provider documentation build status: https://github.com/Teradata/airflow/actions/workflows/ci-teradata-push-branch-documentation-unit-tests.yml

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