API endpoint correctness

API endpoints must behave according to their intended design, properly handling special values and executing expected operations like validation. This includes preserving meaningful null values (e.g., null representing “no limit”) rather than replacing them with default values that change the intended behavior, and ensuring validation runs when expected.

For example, when creating API keys where remaining: null signifies unlimited usage, the endpoint should preserve this null value rather than defaulting to a capped value. Similarly, validation endpoints like isUsernameAvailable should actually execute validation logic rather than bypassing it.

// Good: Preserve meaningful null values
const apiKey = {
  remaining: null // Correctly represents "no cap"
};

// Bad: Replace null with default that changes behavior  
const apiKey = {
  remaining: remaining || defaultLimit // Unintentionally caps usage
};