[python] Refactor signer architecture for REST API authentication

[tonymtu]

Purpose

This PR is the pypaimon implementation of #7100, adding pluggable signer architecture for REST API authentication in the Python client.

Key changes:

• Refactored the authentication module into a cleaner package structure (pypaimon/api/auth/)
• Introduced DLFRequestSigner abstract base class to abstract signing behavior
• Implemented two signing algorithms:
  • DLFDefaultSigner: Original DLF signing algorithm (DLF4-HMAC-SHA256) for VPC endpoints
  • DLFOpenApiSigner: OpenAPI signing algorithm (HMAC-SHA1, ROA v2 style) for AlibabaCloud OpenAPI endpoints (dlfnext)
• Added automatic signer selection based on URI patterns in DLFAuthProviderFactory
• Added new configuration option: dlf.signing-algorithm

Benefits:

• Consistent behavior with Java implementation
• Better extensibility for future signing algorithms

Tests

• Added DLFSignerTest with comprehensive test coverage for both signers
• Verified with real AK and STS credentials against actual DLF endpoints

catalog_options = {
    'metastore': 'rest',
    'warehouse': '${catalog-name}',
    'uri': 'https://dlfnext.${region-id}.aliyuncs.com',
    'token.provider': 'dlf',
    "dlf.access-key-id": "${access-key-id}",
    "dlf.access-key-secret": "${access-key-secret}",
    "dlf.security-token": "${security-token}",
    'dlf.oss-endpoint': 'oss-${region-id}.aliyuncs.com'
}
catalog = CatalogFactory.create(catalog_options)

# table = catalog.get_table('${database-name}.${table-name}')
# read_builder = table.new_read_builder()
# ............

API and Format

N/A

Documentation

N/A - done by #7100

[JingsongLi]

+1