[BUG] Pii-Safe Compiler Plugin — FIR checker not considering Type Arguments annotated with `@PiiSafe.HasPii`

Description

When a data class is NOT annotated with @PiiSafe.HasPii, the FIR checker HasPiiRequiresAnnotatedPropertyChecker verifies if any of its properties are annotated with @PiiSafe.HasPii. However, it is missing checking the Type Arguments as well, leaving the following scenario prone to leaking PII:

@PiiSafe.HasPii
data class MessageAddress(
    @get:PiiSafe.Mask
    val value: String,
    val label: String,
)

data class MessageEnvelope(
    val subject: String,
    val from: List<MessageAddress>,
    ...
)

Expected behaviour

1. Build should fail with the following message:

    > Task :feature:mail:message:api:compileKotlinJvm FAILED
    e: file:///<file-path>/MessageEnvelope.kt:22:5 This class holds a property of a type annotated @PiiSafe.HasPii; this class must also be annotated @PiiSafe.HasPii.
   

2. (In case of enabled) IDE should mark the properties whose type argument is annotated with @PiiSafe.HasPii as an error, showing the above-mentioned message

Actual behaviour

1. The build succeeds
2. No toString method is overridden if no other property type is annotated with @PiiSafe.HasPii
3. (In case of enabled) No IDE error

Build output:

> BUILD SUCCESSFUL

Instructions

• Although this is labelled as good first issue, it involves a complex topic with not much documentation. You may need to check the Kotlin Compiler source code to succeed in this task.
• This is a bug in the newly introduced Kotlin Compiler Plugin, located at library/pii-safe/compiler-plugin
• You will need to change the logic inside the HasPiiRequiresAnnotatedPropertyChecker.check method to look after type arguments.
• You MUST implement test cases to handle this scenario inside HasPiiRequiresAnnotatedPropertyCheckerTest