message: Make disposables comparable (identity check)
diff: namespace caf {
  /// Represents a disposable resource.
  -class CAF_CORE_EXPORT disposable {
  +class CAF_CORE_EXPORT disposable : detail::comparable<disposable> {
  public:
  // -- member types -----------------------------------------------------------
  @@ -114,6 +114,13 @@ public:
  return pimpl_;
  }
  + // -- comparisons ------------------------------------------------------------
  +
  + /// Compares the internal pointers.
  + [[nodiscard]] intptr_t compare(const disposable& other) const noexcept {
  + return pimpl_.compare(other.pimpl_);
  + }
  +
  private:
  intrusive_ptr<impl> pimpl_;
  };
  