@type t() :: %ApolloSignal.Types.CreateContactBody{
  email: String.t(),
  first_name: String.t() | nil,
  last_name: String.t() | nil,
  phone: String.t() | nil,
  properties: %{optional(String.t()) => String.t()} | nil,
  segments: [ApolloSignal.Types.SegmentRef.t()] | nil,
  topics: [ApolloSignal.Types.TopicSubscriptionBody.t()] | nil,
  unsubscribed: boolean() | nil
}