Summary

Add an endpoint that returns similar podcasts based on a given podcast ID.

Endpoint Design

GET /related?id=123456&limit=10

Response:

{
  "related": [
    { "trackId": 789, "trackName": "Similar Podcast", "genre": "Technology" }
  ],
  "sourceId": 123456,
  "matchedBy": "genre"
}

Implementation Notes

• Use iTunes lookup API to fetch podcast details: https://itunes.apple.com/lookup?id={id}
• Match by genre first, then by search term similarity
• Cache aggressively (podcast metadata doesn't change often)
• Consider using genreIds array from podcast metadata

Acceptance Criteria

• /related?id=123 returns similar podcasts
• Returns empty array for invalid/unknown podcast ID
• Respects limit parameter (1-20)
• Response is cached appropriately
• Tests added