Improve configuration error handling of HttpAppender

[Suvrat1629]

This PR introduces improvements to HttpAppender and adds a new test class, HttpAppenderBuilderTest, to enhance test coverage. The changes include:
Updating HttpAppender.java to improve logging behavior.
Adding HttpAppenderBuilderTest.java to verify the builder logic for HttpAppender.
Ensuring that missing configurations (e.g., URL, Layout) correctly log errors.

Fixes #3011

Checklist

• Base your changes on 2.x branch if you are targeting Log4j 2; use main otherwise
• ./mvnw verify succeeds (if it fails due to code formatting issues reported by Spotless, simply run ./mvnw spotless:apply and retry)
• Non-trivial changes contain an entry file in the src/changelog/.2.x.x directory
• Tests for the changes are provided
• Commits are signed (optional, but highly recommended)

[github-actions]

Job	Requested goals	Build Tool Version	Build Outcome	Build Scan®
build-macos-latest	clean install	3.9.8	✅
build-ubuntu-latest	clean install	3.9.8	✅
build-windows-latest	clean install	3.9.8	✅

Generated by gradle/develocity-actions

[ppkarwasz]

There are formatting errors in your PR. Run:

./mvnw spotless:apply

to fix them.

[Suvrat1629]

@ppkarwasz
./mvnw spotless:apply used this and committed the formatting, what else do i need to do in the PR?

[ppkarwasz]

./mvnw spotless:apply used this and committed the formatting, what else do i need to do in the PR?

We have two style rules for the code:

• We use the Palantir Java Formatter. This is what spotless:apply can fix.
• We don't use wildcard imports. You need to configure this in your IDE, e.g. by setting the "Class count to use import with '*'" and related options to 99. I fixed it in ff71db9.

I'll look at your PR in the weekend.

[Suvrat1629]

Yeah I just realized that when i ran mvn clean install, I'll keep in mind to avoid wildcard imports next time.

[Suvrat1629]

@ppkarwasz gentle ping! Could you please take a look :) Thank you!

[ppkarwasz]

Fixes #3011

[ppkarwasz]

@Suvrat1629,

Thank you for your contribution.