Add basic invoices setup

lib/strike_me/api/invoices/invoice.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+module StrikeMe
+  module API
+    class Invoices
+      class Invoice < BaseModel
+        attribute :invoiceId
+        attribute :amount
+        attribute :state
+        attribute :created, :datetime
+        attribute :description
+        attribute :issuerId
+        attribute :receiverId
+        attribute :payerId
+
+        attribute_names.select { _1.end_with? 'Id' }.each do |snake_name|
+          alias_attribute snake_name.underscore, snake_name
+        end
+
+        def paid?
+          state == 'PAID'
+        end
+      end
+    end
+  end
+end