Adding new ExternalAuthProviderError that will be raised when we receive 'problem with LDAP service' response from server.

[petyaslavova]

Pull Request check-list

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Description of change

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[Copilot]

Pull Request Overview

This PR introduces a new ExternalAuthProviderError exception to handle authentication errors from external providers like LDAP. When the Redis server returns a "problem with LDAP service" error message, the client will now raise this specific exception instead of a generic error.

Key changes:

• Added new ExternalAuthProviderError exception class
• Updated error parser to detect and raise the new exception for LDAP service errors
• Added comprehensive test coverage with mock socket implementation

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
redis/exceptions.py	Defines the new ExternalAuthProviderError exception class
redis/_parsers/base.py	Integrates the new exception into the error parsing logic
tests/test_parsers/test_errors.py	Adds test suite with mock Redis protocol implementation
tests/conftest.py	Adds utility function to skip tests when hiredis parser is available

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[Copilot]

[nitpick] Missing decode_responses parameter initialization. Consider explicitly setting this to False or True to make the test's expectations clear and avoid relying on default behavior.

Suggested change

	protocol=protocol_version,
	protocol=protocol_version,
	decode_responses=False,