refactor: simplified network error detection by checking only the NSURLErrorDomain

[duyhungtnn]

Simplified network error detection by checking only the NSURLErrorDomain and handling timeout errors separately. Moved the list of network error codes used for testing from BKTError to BKTErrorTests, and updated related test logic. Improved comments for clarity in error handling.

[Copilot]

Pull Request Overview

This PR simplifies network error detection by treating all NSURLErrorDomain errors as network errors, except for timeout errors which are handled separately. This removes the need to maintain a hardcoded list of specific network error codes in the production code.

• Simplified error handling logic by checking only the NSURLErrorDomain instead of specific error codes
• Moved the network error codes list from production code to test-only code
• Updated test references and improved error handling comments

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
BKTError.swift	Simplified network error detection logic and removed hardcoded network error codes list
BKTErrorTests.swift	Added test-specific network error codes list and updated test references
ApiClientImpl.swift	Enhanced comments for clarity in error handling logic

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