Sets the collection link validations of the amount field. Two validations will always be present in the checkout form amount field:
- The amount must be greater than zero.
- The amount must be within the limits allowed by Mono.
The field "amount_validation" is an additional validation configured to be applied to the checkout form's amount field.
- fixed: No validation will be applied to the amount field in the checkout form, and the user will not be able to enter an amount.
The checkout form's amount field will contain the configured amount (the amount is fixed).
- free: No validation will be applied, and the user can enter any amount in the checkout form.
- can_be_less: The amount entered by the user can be less than or equal to the configured amount.
- can_be_greater: The amount entered by the user can be greater than or equal to the configured amount.