Issue Description

sanitizeValues() tries to mutate the input settings data, which is visible mostly for customAnnotationsMapping and directiveAnnotationsMapping; if the input data is immutable (e.g. supplied via mapOf() etc.), the result is a not-too-helpful UnsupportedOperationException.

The solution would be for the sanitization method to produce a mutated copy of the whole map instead, and re-assign that copy via mappingConfig.setDirectiveAnnotationsMapping() etc. instead of trying to mutate in place.

A worse solution would be to explicitly require a mutable input parameter (e.g. mutable map) in the affected cases, although this would be a serious code smell IMVHO.

Steps to Reproduce

        directiveAnnotationsMapping = mapOf(
            "foo" to listOf(
                "@bar",
            ),
        )

with Kotlin DSL e.g.

Expected Result

Should work.

Actual Result

UnsupportedOperationException due to attempted entry.setValue() on the map.

Your Environment and Setup

• graphql-java-codegen version: 5.8.0
• Build tool: Gradle 8.4
• Mapping Config: see above