OpenSystemsDevelopment / qpdf

…ent and simplified temporary null management. Clean up unused test coverage markers.

Simplify integer value retrieval by introducing a templated `value` method in the `Integer` class. Replace redundant exception handling logic across multiple functions with this unified approach. Streamline type conversions and improve readability.

…` and replace with `String::utf16`.

Added `qpdf::String` class to encapsulate string operations. Updated `QPDFObjectHandle` string methods to utilize `qpdf::String`, streamlined empty string handling, and removed redundant test coverage entries.

…oved shared pointer handling, remove deprecated object methods, and update all references.

Replace `getParsedOffset()` with the new `offset()` method across `QPDFObjectHandle` and related classes for consistent offset handling. Simplify logic and remove redundant `getParsedOffset()` implementation.

Relocate `StreamCopier` to `QPDF::Doc` for improved encapsulation of stream copying functionality. Adjust all references to use the updated placement.

…directives across modules to improve clarity and enforce better assertion practices.

…ator[] for improved consistency and clarity, and remove unused test coverage entry.

…bounds checks with subscript operator, simplify loop logic, and remove redundant trace.

Refactor array handling in `QPDFObjectHandle`: replace `int` with `size_t` for size and index operations, introduce utility functions for type conversions, and simplify sparse array logic.

…`warn`, streamline condition handling.

… warnings, and centralize utility methods.

Introduce null checks for `callbacks` in `QPDFObjectHandle` to allow content streams to be parsed without ParserCallbacks. Update `QPDFJob` to pass `nullptr` instead of `DiscardContents` for parsing.

…std::string_view`, improving performance and code clarity.

…ng encapsulation and maintainability.

…ssing to simplify buffer handling

Simplified checks for empty containers and strings across the codebase using the `.empty()` method. This improves code readability and adheres to best practices for checking emptiness.

Converted multiple occurrences of `count()` to `contains()` throughout the codebase where the goal was to check key existence in containers. This improves code readability and aligns with modern C++ practices, particularly with C++20, making the intent more explicit and potentially aiding performance.

Simplified code by removing redundant `this` qualifiers where they are not essential, improving readability and alignment with coding standards. No changes were made to functionality.

Add static parse methods. Make all external access to QPDFParser through
static methods.

Make all non-static methods including constructors private.

- Add missing export for operator QPDFObjGen.

- Fix handling of indirect references. The use of the type_code method
  in various switch statements bypassed the special handling of
  ::ot_reference objects. Replace with new method resolved_type_code.

Add tests for ::ot_reference objects.

Avoid creating new identical descriptions for each content stream token.

Also remove some shared pointers and use std::string instead of Pl_Buffer
in Pl_QPDFTokenizer.

Add new private Util.hh header to define inline functions and expose as
ordinary functions in QUtil.

- Remove unnecessary QPDF_DLLs
- make deleted constructors public
- move some comments to support tooltips
- modernise some constructors and destructors
- change some member shared pointers to unique pointers