docs: Document outputDirectory and other configuration parameters

[omerazmon-idme]

Summary

This PR documents three configuration parameters that already exist in the plugin code but were not documented in the README:

1. outputDirectory - Control where .ci-friendly-pom.xml is written
2. ciFriendlyPomFilename - Customize the flattened POM filename
3. autoRewriteCiFriendlyPoms - Skip rewrites when POM is up-to-date

Motivation

While investigating how to keep .ci-friendly-pom.xml files out of the workspace root in multi-module projects, I discovered that the outputDirectory parameter already exists in AbstractCiFriendlyMojo but is not documented.

This makes it difficult for users to discover this useful feature.

Changes

• Added Configuration Parameters section to README
• Documented outputDirectory with example showing ${project.build.directory} usage
• Documented benefits: cleaner workspace, no need for .gitignore entries, consistency with Maven practices
• Documented ciFriendlyPomFilename with both POM and command-line examples
• Documented autoRewriteCiFriendlyPoms for build optimization

Testing

I've tested the outputDirectory configuration in a multi-module project and confirmed:

• Setting <outputDirectory>${project.build.directory}</outputDirectory> successfully writes .ci-friendly-pom.xml to the target/ directory
• No .ci-friendly-pom.xml files clutter the workspace
• Maven builds and installs work correctly

Example Usage

<plugin>
  <groupId>com.outbrain.swinfra</groupId>
  <artifactId>ci-friendly-flatten-maven-plugin</artifactId>
  <configuration>
    <outputDirectory>${project.build.directory}</outputDirectory>
  </configuration>
  <executions>
    <execution>
      <goals>
        <goal>clean</goal>
        <goal>flatten</goal>
      </goals>
    </execution>
  </executions>
</plugin>

Related

These parameters have existed since the plugin's initial implementation but were not included in the README documentation.

[Copilot]

Pull request overview

This PR adds documentation for three existing but previously undocumented configuration parameters in the ci-friendly-flatten-maven-plugin: outputDirectory, ciFriendlyPomFilename, and autoRewriteCiFriendlyPoms.

Changes:

• Added a "Configuration Parameters" section to the README with detailed documentation for each parameter
• Included default values, property names, usage examples, and benefits for each parameter
• Positioned the new section between "Plugin setup" and "Plugin Goals" sections

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[Copilot]

Missing blank line before the section heading. For consistency with the rest of the document (e.g., between lines 52 and 54), there should be a blank line between the closing code block and the "## Plugin Goals" heading.

Suggested change

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