In January, add-ons will be merged into a single PRO version of Easy Booking. The price will change from 99€ (for all add-ons) to 79€/year. If you buy any add-on now, you will be able to upgrade for free (without having to renew the license every year). If you want to avoid migration between plugins, you can also wait for the PRO version to be released.
Documentation
Duration Discounts > Developers > Filters
ebdd_booking_duration
Filters booking duration when calculating new price.
Args: (integer) $duration, (array) $booking_data, (integer) $_product_id
easy_booking_settings_capability
Overrides the default capability level to access the Easy Booking settings page (default to “manage_options”).
Args: (string) $capability