chore: add installments api resource

lib/asaas/object_types.rb

@@ -24,6 +24,7 @@ def self.object_names_to_classes
         Card::OBJECT_NAME => Card,
         CashBalance::OBJECT_NAME => CashBalance,
         Charge::OBJECT_NAME => Charge,
+        Installment::OBJECT_NAME => Installment,
         CountrySpec::OBJECT_NAME => CountrySpec,
         Coupon::OBJECT_NAME => Coupon,
         CreditNote::OBJECT_NAME => CreditNote,

lib/asaas/resources.rb

@@ -15,6 +15,7 @@
 require "asaas/resources/card"
 require "asaas/resources/cash_balance"
 require "asaas/resources/charge"
+require "asaas/resources/installment"
 
 require "asaas/resources/country_spec"
 require "asaas/resources/coupon"

lib/asaas/resources/installment.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+module Asaas
+  # TODO: doc.
+  class Installment < APIResource
+    extend Asaas::APIOperations::Search
+    include Asaas::APIOperations::Save
+    extend Asaas::APIOperations::List
+
+    OBJECT_NAME = "installment"
+
+    def self.resource_url
+      "/v3/installments"
+    end
+
+    def resource_url
+      "/v3/installments/#{CGI.escape(id)}"
+    end
+
+    def self.payments(installment, params = {}, opts = {})
+      request_asaas_object(
+        method: :get,
+        path: format("/v3/installments/%<installment>s/payments", { installment: CGI.escape(installment) }),
+        params: params,
+        opts: opts
+      )
+    end
+  end
+end