v0.1.3

Fixed

• close_position rejected with validation.null-not-allowed.request.
  IG silently drops the body of real DELETE requests, so every
  required field on ClosePositionRequest was reported as null. The
  transport now mirrors the official Python trading-ig client and
  rewrites body-carrying DELETEs as POST with an _method: DELETE
  header. Bodyless DELETEs (session logout, watchlists delete,
  workingorders delete) are untouched. Validated live on a demo
  account: position fully closed, expected P/L confirmed.
• Defence in depth: ClosePositionRequest now carries
  #[serde(skip_serializing_if = "Option::is_none")] on every optional
  field, so explicit nulls never reach IG even if a future code path
  bypasses the transport rewrite.

Added

• examples/diag_close_position.rs — list open positions and close the
  first, logging the outbound JSON. Handy when reproducing the
  null-not-allowed bug or validating the rewrite against a fresh demo
  account.
• tests/dealing_positions.rs::close_position_rewrites_delete_to_post_with_method_override
  pins the rewrite + asserts the JSON body survives intact.
• tests/support/matchers::HasMethodOverride and
  IgMockServer::mount_delete_error helpers for tests that target
  body-carrying DELETE endpoints.