OpenSystemsDevelopment / qpdf

…ctionary key access, and simplify null handling logic.

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.

Move all dictionary specific methods to BaseDictionary. Create new subclass
Dictionary to allow QPDFObjectHandle to access the moved methods.

The new class is only usable as base classes and does not support direct
instantiation or upcasting.

Add operators to convert to bool, QPDFObjectHandle and QPDFObjGen.

Derive QPDFObjectHandle from BaseHandle and make final.

Provide a custom method to check whether a name is valid utf8. Integrate
checking for characters that need to be escaped in JSON.

Create an alternative to getJSON to allow an object handle to be written as JSON without the overhead of creating a JSON object.

Use move semantics for dictionary creation.

Remove parameters and return the description.

Add optional parameter shallow. Change logic errors to runtime errors.

QPDFValueProxy wasn't a good name for it. We decided the evil of
having the header file be named QPDFObject_private.hh was less than
the evil of having the class be named something other than what it
should have been named.

I decided that it's actually fine to copy a direct object to another
QPDF. Even if we eventually prevent a QPDFObject from having multiple
parents, this could happen if an object is moved.

This is in preparation for restoring a QPDFObject.hh to ease the
transition on qpdf_object_type_e.

This commit was created by
* Renaming QPDFObject.cc and QPDFObject.hh
* Replacing QPDFObject\b with QPDFValueProxy (where \b is word
  boundary)
* Running format-code
* Manually resorting files in libqpdf/CMakeLists.txt
* Manually refilling the comment in QPDF.hh near class Resolver

On destruction of the QPDF object replace all indirect object references
with direct nulls.

Remove all existing code to release resolved references.

Fixes performance issue due to interaction of resetting QPDFValue::qpdf and
og members and prior code.

Move responsibility for creating shared pointers to objects and cloning from QPDFObjectHandle to QPDFObject.

There are no automated tests yet, but committing work so far in
preparation for some refactoring.

Update getJSON() methods and calls to them

Where not possible, use "auto" to get the iterator type.

Editorial note: I have avoid this change for a long time because of
not wanting to make gratuitous changes to version history, which can
obscure when certain changes were made, but with having recently
touched every single file to apply automatic code formatting and with
making several broad changes to the API, I decided it was time to take
the plunge and get rid of the older (pre-C++11) verbose iterator
syntax. The new code is just easier to read and understand, and in
many cases, it will be more effecient as fewer temporary copies are
being made.

m-holger, if you're reading, you can see that I've finally come
around. :-)

Change .clang-format and commit automated changes from a fresh run of
format-code

Make it so that a key with a null value is always treated as not being
present. This was inconsistent before.