Updated the 'canUsedInOrder' function in Discount.php to accept ERP Entity Interface arguments
instead of Order Interfaces for better flexibility and compatibility. Added checks to ensure that
the provided entity is an instance of the Order Interface, increasing robustness.

This commit fixes several issues in different PHP files.
- Added `method_exists` checks for `isActive` method in `activate.php`, `deactivate.php` and
`toggle.php` to prevent calls to an undefined method.
- Similar check added for `getTitle` method in `get.php`.
- Fixed sorting functionality in `search.php` by using `strcmp` instead of greater than comparison.
- Removed a large number of ignored errors in `phpstan-baseline.neon`, indicating reduced error
handling.
- Corrected the `implode` parameters order in `Discount.php` and typecasted variable to string
before using `explode` in `PriceFactor.php`.
- Updated `getTitle` & `toPriceFactor` method parameters in `Discount.php` to use union types for
compatibility with different data types.

Related: #18

refactor: isDiscountUsableWithQuantity isDiscountUsableWithPurchaseValue are public now, usable as api