@type segment() :: String.t() | atom()

A segment of a topic. A string is a literal, and an atom is a param.

@type t() :: %VerifiedPubSub.Dsl.Topic{
  __identifier__: term(),
  __spark_metadata__: term(),
  description: String.t() | nil,
  messages: [VerifiedPubSub.Dsl.Message.t()],
  name: atom(),
  params: [atom()],
  segments: [segment()]
}

The fields of the topic:

• name: the name that call sites use.
• segments: the segments of the wire topic.
• description: the description, or nil.
• params: the params, in the order of the segments.
• messages: the events of the topic.
• __identifier__ and __spark_metadata__: Spark sets these.