Refactor Logger level checks and encapsulate Response.Builder fields

[saikat709]

Refactors logging level comparisons and encapsulates Response.Builder fields for better API hygiene.

Summary of Changes

• Logger.Level#atLeast: Adds atLeast(Level other) helper to Logger.Level and replaces ordinal() comparisons across Logger.java.
• Logger helper extraction: Splits logAndRebufferResponse into logResponseHeaders and rebufferBody private helpers.
• Response.Builder encapsulation: Makes Builder fields private (status, reason, headers, body, request).

Tests Added

• LoggerMethodsTest: Adds tests for Logger.Level.atLeast() covering equal, more verbose, and less verbose level comparisons.

$ ./mvnw test -pl core -Dtest=LoggerMethodsTest,LoggerTest,LoggerRebufferTest -Dtoolchain.skip=true
Tests run: 11, Failures: 0, Errors: 0, Skipped: 0

[velo]

The Level.atLeast() extraction is a good, well-named improvement over the scattered ordinal() comparisons, and shortening logAndRebufferResponse by pulling out logResponseHeaders/rebufferBody is a reasonable move. A few things need fixing before merge:

1. The six new Response.Builder getters aren't needed. Builder is a static nested class of Response, so the enclosing class already has access to its private fields directly — I verified this compiles fine (mvn -pl core compile) with the getters removed and the constructor reading builder.status/builder.request/etc. directly. The getters add a second, wider access surface (package-visible, no benefit) and collide in name with the existing fluent setters (status() getter vs status(int) setter). Please drop them and keep direct field access from the constructor — the private modifier change alone already achieves the stated goal.

2. logResponseHeaders(String, Level, Response) takes a logLevel parameter that's never used — the caller already gates the call behind logLevel.atLeast(Level.HEADERS). Please drop the unused parameter.

3. One spot wasn't converted to the new abstraction: logLevel.compareTo(Level.NONE) > 0 should be logLevel.atLeast(Level.BASIC), consistent with the rest of the refactor.

4. LoggerMethodsTest.java currently fails the project's own formatting check (git-code-format-maven-plugin / verify-formatting) — there's a stray trailing-whitespace-only blank line before one of the new @test methods. This will fail CI as-is; please run the formatter.

Happy to merge once these are addressed.