Make lock key prefix configurable (currently hardcoded php-malkusch-lock)

[mkduew]

Currently, the lock key prefix is hardcoded in LockUtil:

final public function getKeyPrefix(): string
{
    return 'php-malkusch-lock';
}

This makes it impossible to configure or shorten the prefix from the outside.

Problem

This is especially problematic when using MySQLMutex, because:
• MySQL limits GET_LOCK() names to 64 characters
• The default prefix php-malkusch-lock already consumes 17 characters
• This significantly reduces the usable length for application-specific lock keys
• In practice, this can easily lead to unexpected failures when keys are generated dynamically

Why configurability matters

Being able to configure the prefix would allow:
• Shorter prefixes when strict limits apply (e.g. MySQL)
• Custom prefixes to avoid collisions between applications
• More flexibility for users who already manage namespacing on their own

Suggested solution

One of the following (or similar) approaches would be very helpful:
• Allow passing a custom key prefix via constructor / configuration
• Provide a setter or optional parameter for LockUtil
• Or make the prefix overridable instead of hardcoded

This would be particularly useful in combination with MySQLMutex, where every character counts.

Thanks a lot for your work on this library, and happy to provide more context or examples if needed!

[mvorisek]

PR with a test showing the actual problem is welcomed.