v0.4.0

Changed

• BREAKING: Renamed "anchor" to "controller versionId" throughout the
  library. VerifiedResourceLog.headAnchorIndex is now
  headControllerVersionIndex; the admitAppend hook input's anchor and
  anchorIndex are now controllerVersionId and controllerVersionIndex.
  Integrity error messages that referred to an entry's "anchor" now refer to its
  controller versionId. Docs use "controller versionId" in place of "anchor".
• Docs and code now call the verifier's running controller version the "head
  controller version" (was "version floor"); the ARCHITECTURE.md glossary entry
  is renamed. No API change.
• BREAKING: an entry's proofs must all carry the same controller versionId
  and be by distinct signing keys. A log whose entry carries divergent
  controller versionIds or a repeated signing key is now refused from genesis as
  ResourceLogIntegrityError; the client's held pin stays where it was, and
  there is no in-library heal for that shape (only a hand-built log can carry
  it). assertionMethod membership is checked at the entry's controller
  versionId for every proof, once per entry, instead of at each proof's own. The
  admitAppend hook input's controllerVersionId and controllerVersionIndex
  are now the entry's controller version for every proof, and the input gains
  proofKeys: every proof's signing-key multibase, distinct, in array order. A
  consumer that constructs the hook input directly (rather than receiving it
  from the library) must add proofKeys, and a hook must return the same
  verdict regardless of proofKeys order, since the proof array is not
  integrity-bound. The verifier now makes one assertionKeysAt call per entry
  instead of one per proof.

Fixed

• appendResourceLog now treats an empty etag from store.read as no
  validator and refuses to write, instead of sending a blank If-Match.
• The entry builders now refuse a null or undefined state with the intended
  misuse Error instead of a TypeError. The builders and the reader's entry
  shape check share one state-document rule.