DOC: Resolve build warnings

[stefan6419846]

This fixes #1941 by cleaning up wrong references and adding new docs. Some notes about this:

• Building the docs now works without prior package installation.
• The intersphinx mapping will now always use the objects of the Python version used for the docs build.
• The intersphinx mapping for Pillow has been added.
• Links to private methods in the developer docs have been replaced by inline code as they are not part of the Sphinx docs.
• Some broken/outdated/strange docstrings have been fixed.
• New classes have been added to the docs. Module-specific classes have been added to the modules where they are being used directly, some generic classes/modules have been put into new files/pages.
• We have to exclude some members to avoid duplicate definitions.

Current output:

(venv) stefan@localhost:~/temp/pypdf> rm -rf build/ && LANG=C sphinx-build -n -T -b html docs build/sphinx/html
Running Sphinx v7.2.6
making output directory... done
loading intersphinx inventory from https://docs.python.org/3.9/objects.inv...
loading intersphinx inventory from https://pillow.readthedocs.io/en/latest/objects.inv...
[autosummary] generating autosummary for: dev/cmaps.md, dev/deprecations.md, dev/documentation.md, dev/intro.md, dev/pdf-format.md, dev/pypdf-parsing.md, dev/pypdf-writing.md, dev/releasing.md, dev/testing.md, index.rst, ..., user/metadata.md, user/migration-1-to-2.md, user/pdf-version-support.md, user/pdfa-compliance.md, user/post-processing-in-text-extraction.md, user/reading-pdf-annotations.md, user/robustness.md, user/streaming-data.md, user/suppress-warnings.md, user/viewer-preferences.md
myst v2.0.0: MdParserConfig(commonmark_only=False, gfm_only=False, enable_extensions=set(), disable_syntax=[], all_links_external=True, url_schemes=('http', 'https', 'mailto', 'ftp'), ref_domains=None, fence_as_directive=set(), number_code_blocks=[], title_to_header=False, heading_anchors=0, heading_slug_func=None, html_meta={}, footnote_transition=True, words_per_minute=200, substitutions={}, linkify_fuzzy_links=True, dmath_allow_labels=True, dmath_allow_space=True, dmath_allow_digits=True, dmath_double_inline=False, update_mathjax=True, mathjax_classes='tex2jax_process|mathjax_process|math|output_area', enable_checkboxes=False, suppress_warnings=[], highlight_code_blocks=True)
building [mo]: targets for 0 po files that are out of date
writing output... 
building [html]: targets for 57 source files that are out of date
updating environment: [new config] 57 added, 0 changed, 0 removed
reading sources... [100%] user/viewer-preferences
looking for now-outdated files... none found
pickling environment... done
checking consistency... done
preparing documents... done
copying assets... copying static files... done
copying extra files... done
done
writing output... [100%] user/viewer-preferences
/home/stefan/temp/pypdf/pypdf/xmp.py:docstring of pypdf.xmp.XmpInformation.rdfRoot:1: WARNING: py:class reference target not found: xml.dom.minidom.Element
generating indices... genindex py-modindex done
highlighting module code... [100%] pypdf.xmp
writing additional pages... search done
copying images... [100%] user/nup-dest2.png
dumping search index in English (code: en)... done
dumping object inventory... done
build succeeded, 1 warning.

The HTML pages are in build/sphinx/html.

The remaining issue is about

pypdf/pypdf/xmp.py

Lines 228 to 231 in a91e9f6

	@property
	def rdfRoot(self) -> XmlElement: # deprecated
	deprecate_with_replacement("rdfRoot", "rdf_root", "4.0.0")
	return self.rdf_root

scheduled for removal in version 4.0.0 where I could not find a clean/nice solution for now.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (a91e9f6) 94.35% compared to head (c3d559c) 94.35%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2380   +/-   ##
=======================================
  Coverage   94.35%   94.35%           
=======================================
  Files          43       43           
  Lines        7584     7584           
  Branches     1519     1519           
=======================================
  Hits         7156     7156           
  Misses        265      265           
  Partials      163      163           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[MartinThoma]

Very nice work!

I'm not quite sure yet if we want to document all of those publicly (e.g. the protocols), but we can make them private again if people get confused.

[stefan6419846]

We need them to due to type hints, thus there is not much to do here unfortunately.