Enhance index hint validation for multiple indexes

[FlexIDK]

#58504

[Copilot]

Pull request overview

Updates MySQL index hint validation to support specifying multiple indexes in a single hint string (e.g., useIndex('user_id, PRIMARY')), addressing #58504.

Changes:

• Splits the provided index hint string on commas and validates each index name individually.
• Preserves existing SQL generation while allowing comma/whitespace-separated index lists.

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[Copilot]

The new comma-separated index parsing/validation should be covered by a unit test (e.g., useIndex('user_id, PRIMARY') producing use index (user_id, PRIMARY)), since tests/Database/DatabaseQueryBuilderTest.php currently only asserts single-index behavior for MySQL. Adding a test will prevent regressions and clarify intended whitespace/comma handling.

[shaedrich]

It would probably be better if an array could be passed

[shaedrich]

You could use first-class callable notation here:

Suggested change

	$indexes = array_map('trim', explode(',', $index));
	$indexes = array_map(trim(...), explode(',', $index));

[shaedrich]

It would be helpful to know which index was the problem:

Suggested change

	throw new InvalidArgumentException('Index name contains invalid characters.');
	throw new InvalidArgumentException('Index name "' . $idx . '" contains invalid characters.');