Enable Jackson 3 - Phase 2

[pvillard31]

Description

See #2173 for the initial PR and associated discussion.

This PR is the follow-up of #2182.

• Design GitHubJackson interface with methods for reading/writing JSON Implement GitHubJackson2 and GitHubJackson3
• Create DefaultGitHubJackson factory with programmatic selection
• Create GitHubJacksonException wrapper classes
• Add GitHubBuilder.withJackson() for configuring Jackson implementation
• Add testing infrastructure for both Jackson versions

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• Changes must not break binary backwards compatibility. If you are unclear on how to make the change you think is needed while maintaining backward compatibility, CONTRIBUTING.md for details.
• Add JavaDocs and other comments explaining the behavior.
• When adding or updating methods that fetch entities, add @link JavaDoc entries to the relevant documentation on https://docs.github.com/en/rest .
• Add tests that cover any added or changed code. This generally requires capturing snapshot test data. See CONTRIBUTING.md for details.
• Run mvn -D enable-ci clean install site "-Dsurefire.argLine=--add-opens java.base/java.net=ALL-UNNAMED" locally. If this command doesn't succeed, your change will not pass CI.
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  • If this PR fixes one or more issues, include "Fixes #" lines for each issue.
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[bitwiseman]

Suggested change

	private static final GitHubJackson2 JACKSON2_STATIC = new GitHubJackson2();
	private static final GitHubJackson2 JACKSON_STATIC = new DefaultGitHubJackson.createDefault();

[pvillard31]

The JACKSON2_STATIC field is intentionally typed as GitHubJackson2 because it's used by the static methods getMappingObjectReader() and getMappingObjectWriter() which return Jackson 2.x specific types (com.fasterxml.jackson.databind.ObjectReader/ObjectWriter).

If we change this to use DefaultGitHubJackson.createDefault(), it would return GitHubJackson3 when Jackson 3 is available, which would break these methods since they need Jackson 2.x types.

Should we:

• Keep JACKSON2_STATIC as-is for backward compatibility with these static methods?
• Deprecate these Jackson 2.x specific static methods?
• Something else?