Allow tenants to commit to a certain period (e.g. 6 or 12 months) and receive a discount for that commitment.

The commitment is NOT a prepayment. Instead, tenants receive a discount by agreeing to commit themselves for a certain period.

This feature could reuse elements of the "prepayment" feature, i.e.:

• let the operators decide if they want to offer prepayments, commitments, or neither
• let the operator define the commitment periods (always 1 month, plus e.g. 6, 12, or others)
• for every period, let them define a title, description and promo code that is auto-applied

Commitments should be correctly communicated in the booking summary in the customer portal.