Disambiguate projection parameters when input argument is named _alias or _projection - #997

Fixes #930

Root Cause

In Kotlin 2 client generation (GenerateKotlin2ClientTypes.kt), projection methods for complex fields add:

1. Every input argument defined on the GraphQL field via addInputArgs.
2. A client-side field alias parameter hardcoded as _alias: String? = null.
3. A client-side projection lambda parameter hardcoded as _projection: TypeProjection.() -> TypeProjection.

When a GraphQL schema field has an argument named _alias (or _projection), the generated method ends up with two parameters sharing the same identifier, resulting in a Kotlin compilation failure (Conflicting declarations: _alias) as well as ambiguous symbol references when constructing the field(...) call.

Solution

• When adding the client projection parameters for a field, check the sanitized names of inputValueDefinitions.
• Disambiguate the alias parameter name (appending trailing underscores, e.g. _alias_) and projection parameter name (_projection_) only if they collide with an input argument on that field.
• For all existing schemas without colliding arguments, the parameter names remain unchanged (_alias and _projection), preserving full backward compatibility.
• Added unit tests in Kotlin2CodeGenTest asserting correct code generation and compiling client queries that use _alias and _projection field arguments.

Local Verification

Executed ./gradlew check with OpenJDK 17:

BUILD SUCCESSFUL in 5m 44s
49 actionable tasks: 26 executed, 23 up-to-date