@spec attribute(RevenueCat.Customer.t(), String.t() | atom()) ::
  RevenueCat.Customer.Attribute.t() | nil

Fetch a single customer attribute struct by name.

@spec current_offering(RevenueCat.Offerings.t()) ::
  RevenueCat.Offerings.Offering.t() | nil

Fetch the current offering struct from an Offerings struct.

@spec entitlement(RevenueCat.Customer.t() | map(), String.t() | atom()) ::
  RevenueCat.Customer.Entitlement.t() | nil

Fetch a single entitlement struct by id.

@spec entitlements(RevenueCat.Customer.t()) :: map()

Return the entitlements map from a customer.

Returns an empty map for non-customer inputs.

@spec fetch_customer(String.t()) :: {:ok, RevenueCat.Customer.t()} | {:error, term()}

Fetch a customer by app user id, bypassing the customer cache.

@spec fetch_offerings(
  String.t(),
  keyword()
) :: {:ok, RevenueCat.Offerings.t()} | {:error, term()}

Get Offerings for a given app_user_id.

This endpoint can optionally take a :platform (string) which will be sent as the X-Platform header (lower-cased to x-platform), e.g. "ios".

@spec get_customer(String.t()) :: {:ok, RevenueCat.Customer.t()} | {:error, term()}

Get a customer by app user id, using the customer cache when possible.

@spec has_entitlement?(RevenueCat.Customer.t(), String.t() | atom()) :: boolean()

Return true if the customer has the given entitlement id.

@spec has_subscription?(RevenueCat.Customer.t(), String.t() | atom()) :: boolean()

Return true if the customer has the given subscription id.

@spec offering(RevenueCat.Offerings.t(), String.t() | atom()) ::
  RevenueCat.Offerings.Offering.t() | nil

Fetch a single offering struct by id from an Offerings struct.

@spec subscription(RevenueCat.Customer.t(), String.t() | atom()) ::
  RevenueCat.Customer.Subscription.t() | nil

Fetch a single subscription struct by id.

@spec subscriptions(RevenueCat.Customer.t()) :: map()

Return the subscriptions map from a customer.

Returns an empty map for non-customer inputs.

@spec update_customer_attributes(String.t(), map()) ::
  {:ok, RevenueCat.Customer.t()} | {:error, term()}

Update customer attributes and return the updated customer.