Enforce strong optional types

Use strong typing and early validation to handle optional values and prevent null-related issues. Prefer enums and specific types over strings when dealing with optional data, and validate optional values as early as possible in the data flow.

Key practices:

1. Use enums instead of strings for known value sets
2. Leverage bool::then for cleaner optional handling
3. Validate optional data at structure boundaries

Example: ```rust // Instead of struct Config { kind: String, // Could be “realm” or “index” value: Option }

// Prefer enum ConfigKind { Realm(String), Index(String) } struct Config { kind: ConfigKind, value: Option }

// Use bool::then for cleaner optional handling let value = condition.then(|| compute_value());

// Validate optional data early fn get_project_version(doc: &mut Document) -> Result<Version, Error> { let project = doc.get(“project”) .ok_or(Error::MissingProject)?;

let version = project
    .get("version")
    .and_then(Item::as_value)
    .and_then(Value::as_str)
    .ok_or(Error::MissingVersion)?;

Version::from_str(version) }