pypresscart 0.1.6

Fixed

• client.campaigns.create() now sends the nullable body fields
  (description, keywords, target_audience, tone, writing_samples,
  file_id) as explicit nulls instead of dropping them. POST /campaigns
  requires these keys to be present in the payload even when null;
  _serialize previously used exclude_none=True unconditionally, so a
  CampaignCreateRequest built with the nullable fields left at their
  None defaults produced a payload the API rejected. _serialize now
  takes an exclude_none keyword (default True, unchanged for every
  other endpoint); campaigns.create opts into exclude_none=False.
  Plain dict bodies are still passed through untouched.