v10.3.0

• DecryptedMessage is now an enum with Text, Commit, and Proposal variants. For migration, see the migration
  guide.

• Fixes a bug which caused stored Proteus sessions to be established afresh rather than loaded, discarding the session
  state already in the database. Every release from v10.0.0 through v10.2.0 is affected.

  Proteus sessions are keyed by a text identifier, which the generated lookup query bound as binary data. SQLite never
  considers a binary value equal to a text one, so the query matched no rows, and a stored session appeared not to
  exist. CoreCrypto holds up to 200 recently used sessions in memory, which hid this until that cache went cold: on a
  restart, on a new CoreCrypto instance, or once more than 200 sessions had been used. Code which asks
  proteusSessionExists before deciding whether to establish a session — as proteusDecryptSafe does — was answered
  "no" for every stored session, and the replacement session it then established overwrote the state that was in the
  database all along. The same fault caused proteusSessionDelete to delete nothing while reporting success, and
  affected lookups of CRLs and E2EI intermediate certificates by their string identifiers.

  CoreCrypto cannot repair an affected database. It has no way to distinguish a session which ought to still be there
  from one whose deletion silently failed, and overwritten session state is not recoverable. Clients which have that
  context may wish to implement a repair pass of their own.

• proteusSessionExists now returns an error, rather than false, when a session is stored but cannot be loaded.
  Treating a failed load as an absent session is what allowed the bug above to overwrite live state, so code which
  establishes a session in response to false no longer does so in that case. proteusDecryptSafe likewise returns the
  error instead of establishing a replacement session.