APIs added/updated:

Add a one time charged to the subscription which will be added to the invoice generated at the end of the current term. See https://apidocs.chargebee.com/docs/api/subscriptions#add_charge_at_term_end.

Add a "non-recurring addon" charge to a subscription which will be added to the invoice generated at the end of the current term. See https://apidocs.chargebee.com/docs/api/subscriptions#charge_addon_at_term_end.

Return an estimate of the amount that will be charged when the subscription renews. See https://apidocs.chargebee.com/docs/api/estimates#subscription_renewal_estimate

Now plans supports charge model to specify how the subscription plan charges should be calculated. See https://apidocs.chargebee.com/docs/api/plans#plan_attributes

Include delayed charges while calculating the Estimate.
Updated gemspec.
Release 1.4.3