Parse EPUB 2 guide as EPUB 3 landmarks

[mickael-menu]

Added

Streamer

• The EPUB 2 <guide> element is now parsed into the RWPM landmarks subcollection when no EPUB 3 landmarks navigation document is declared.

[Copilot]

Pull Request Overview

This PR adds support for parsing EPUB 2 guide elements as a fallback for landmarks when no EPUB 3 navigation document is supplied.

• Adds a new test (testParseEPUB2GuideAsLandmarks) to verify the parsing of the EPUB 2 guide as landmarks.
• Updates the OPFParser to include the EPUB 2 guide in its returned Package and revises the EPUBManifestParser to integrate this fallback behavior.
• Introduces a new String extension (orNilIfBlank) used throughout for clearer blank-checking.

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
Tests/StreamerTests/Parser/EPUB/EPUBManifestParserTests.swift	Added new test for EPUB 2 guide parsing as landmarks.
Tests/StreamerTests/Fixtures/OPF/guide-epub2.opf	Added fixture representing an EPUB 2 package with a guide element.
Sources/Streamer/Parser/EPUB/OPFParser.swift	Updated to return a Package including the new epub2Guide property and added a new parseEPUB2Guide() function.
Sources/Streamer/Parser/EPUB/Extensions/LinkRelation+EPUB.swift	Updated initializers to use clearer parameter names and added an initializer for EPUB 2 types.
Sources/Streamer/Parser/EPUB/EPUBManifestParser.swift	Adjusted parsing logic to integrate the EPUB 2 guide when landmarks are absent.
Sources/Shared/Publication/Services/Content/Iterators/HTMLResourceContentIterator.swift	Refactored blank-checking by replacing takeUnlessBlank() with orNilIfBlank().
Sources/Internal/Extensions/String.swift	Added orNilIfBlank method for enhanced string validation.
CHANGELOG.md	Documented the change regarding streaming EPUB 2 guides as landmarks.

Comments suppressed due to low confidence (1)

Sources/Streamer/Parser/EPUB/OPFParser.swift:85

• [nitpick] The property name 'epub2Guide' clearly indicates its purpose, but for consistency and clarity it might be worth considering a renaming (e.g., to 'epub2GuideLinks') so that it aligns with other link collections like readingOrder and resources.

let epub2Guide: [Link]