add a SEL function to check if a param exists and improve the SEL doc

[jun-he]

Pull Request type

• Bugfix
• Feature
• Refactoring (no functional changes, no api changes)
• Build related changes (Please run ./gradlew build --write-locks to refresh dependencies)
• Other (please describe):

NOTE: Please remember to run ./gradlew spotlessApply to fix any format violations.

Changes in this PR

add a SEL function to check if a param exists and improve the SEL doc

[Copilot]

Pull Request Overview

This PR introduces a new SEL function containsKey to check if a parameter exists, adds corresponding tests, and updates the SEL documentation.

• Added containsKey handling in SelParams.call
• Added unit tests for containsKey in SelParamsTest
• Expanded docs with containsKey in class-function.md

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
netflix-sel/src/main/java/com/netflix/sel/type/SelParams.java	Added containsKey branch to call method
netflix-sel/src/test/java/com/netflix/sel/type/SelParamsTest.java	New tests for containsKey behavior
netflix-sel/docs/lang-guide/class-function.md	Documentation for containsKey function

Comments suppressed due to low confidence (3)

netflix-sel/src/test/java/com/netflix/sel/type/SelParamsTest.java:61

• Add a test case for calling containsKey with an incorrect number of arguments (e.g. zero args) to verify it throws UnsupportedOperationException, mirroring the existing testInvalidCallGet.

}

netflix-sel/docs/lang-guide/class-function.md:195

• [nitpick] Grammar: change “currently only support string type” to “currently only supports string types” for clarity.

return params.getFromSignalOrDefault('signal1', 'param1', 'value1');    // returns parameter param1's value from signal1, if there is any exception, then return the default value (currently only support string type)

netflix-sel/src/main/java/com/netflix/sel/type/SelParams.java:50

• Indent this else if and its closing brace consistently with the surrounding if/else blocks to match the project’s formatting conventions (run spotlessApply to fix).

} else if (args.length == 1 && "containsKey".equals(methodName)) {