not implemented: feedgen auth special-case

Description

Authenticated Bluesky feed generators do not work:

• https://bsky.app/profile/did:plc:ca4b3evcz7rjhni6mngjwfzl/feed/your-pds
  • Returns Message from server: jwt audience does not match (expected did:web:feeds.this-is-epic.space)
• https://bsky.app/profile/did:plc:mn45tewwnse5btfftvd3powc/feed/rinds
  • Returns Message from server: Upstream server responded with a 401 error

Context

• Revision efd499bb264fe6c02e103cac8644cb9f0be3de67
• Discord conversation