async_api_spex-v0.2.0

Added

• use AsyncApiSpex.Schema, fields: [...] derives a schema from an existing
  defstruct; every struct key becomes a property and fields: refines it
  with a type, required, and a description. title: and description:
  describe the schema.
• use AsyncApiSpex.Channel declares a channel, the server it lives on, and
  its operation on the module that publishes to it or consumes from it.
• use AsyncApiSpex.Spec implements spec/0 by assembling a document from
  channel modules, listed with channels: or discovered with otp_app:.
• AsyncApiSpex.Plug.Viewer serves an HTML page that renders a document in
  the browser with the AsyncAPI React component (pinned to 3.2.1 on unpkg;
  :bundle_url and :stylesheet_url point it at a self-hosted copy). Mount it
  next to AsyncApiSpex.Plug.RenderSpec with path: set to that mount.
• CI scaffolds a fresh mix new app that depends on nothing but this library
  and plug, decorates a producer and a consumer, and serves, validates, and
  writes the document, so the library is proven outside the repository it
  lives in.

Changed

• use AsyncApiSpex.Schema without :schema or :fields now raises
  "requires exactly one of :schema or :fields".
• AsyncApiSpex.validate/1 is stricter. A document with a component
  schema that holds a module that does not use AsyncApiSpex.Schema now fails
  validate/1 and mix async_api_spex.gen.

Fixed

• A schema that references itself no longer makes the resolver loop forever.