v0.6.0

• ParameterSerializer emits the wire format the specification declares for
  label and the delimited styles (#45), matching the parser fix in
  rasuvaeff/openapi-contract 0.4.0 — which this package now requires
  (^0.4, was ^0.3). An unexploded label array is comma-separated
  (.blue,black,brown), not dot-separated; spaceDelimited emits the
  separator as %20, since a raw space is not a legal URI character. The two
  packages carried mirror-image bugs, so they agreed with each other and every
  generated request was accepted by the oracle while no conforming server would
  have taken it. Generating a list item that contains its own separator now
  fails closed as UnsupportedGeneration: the styles have no escape for one,
  so such a value has no representation on the wire.
• An optional multipart/form-data request body generates instead of throwing
  LogicException from inside the arbitrary (#41). The "body present" branch of
  an optional body wrapped the generated body and read its shape back, and that
  read accepted the json and form encodings only — multipart carries parts
  rather than a value. The optional form now picks between the body arbitrary
  and no body at all, so nothing re-reads a shape the generator just built.
  Every multipart fixture declared required: true, which is why the hole was
  invisible.
• A negative type-mismatch witness is built only for a parameter with a single
  declared type (#42). An OAS 3.1 union admits every type it lists, so
  not-null is a valid value for ["string", "null"] — the "invalid" case was
  valid and falsified the whole negative phase. ResponseTargets already
  required a single type; the parameter side now agrees.
• The JSON body encoder reads the additionalProperties schema for a key
  outside properties (#43). Losing it encoded a nested empty object as []
  instead of {}, and the contract correctly rejected the result — surfacing as
  invalidGeneratedRequest on a valid contract.
• allOf merges OAS 3.0 nullable as an intersection (#44): null is generated
  only where every branch admits it. Merging it as an ordinary last-write key
  let {type: string, nullable: true} next to {type: string, minLength: 3}
  generate null, which the second branch rejects. A branch omitting nullable
  now counts as nullable: false, which is what OAS 3.0 means by it. The OAS
  3.1 spelling of the same shape (type: [..., "null"] in one branch only)
  already failed closed as conflicting types.