Podcasts - Full Chapter Support

[danieljsummers]

Building on #5, provide a means for users to specify chapters for the media associated with a post (episode).

• Define chapters per episode (see the spec for allowed fields).
• Define a handler for each post that is accessed via /chapters/[permalink] and produces JSON chapters.
• If no chapter metadata is specified, but chapters have been defined, return this link in the podcast:chapters element for the episode.
• Provide a JSON chapter import feature, if the chapters were developed elsewhere and need to be imported.

(There may be other issues created to tackle some of these in bite-sized parts.)

[danieljsummers]

This is complete, and will be a part of v2.1