v0.4.0

• Switch to new chain transport leveraging public Nostr threads
• Add plaintext_hash to Identity, Company and Bill Blocks, which is a hash over the plaintext data
  • (breaks all chains in the DB)
• Add functionality for sharing a bill with an external party, encrypted, hashed, and signed, with the plaintext block data
• Change visibility of bill_service::error and bill_service::service to private, moving the used types to bill_service
• Add cargo deny

Version: v0.4.0