//! Serde helper modules for common API wire-format patterns.
//!
//! Each module is designed to be used with `#[serde(with = "...")]`.
//!
//! | Module | Use case |
//! |-----------------|--------------------------------------------------------|
//! | [`json_string`] | Value ↔ stringified JSON (`"{\"k\":\"v\"}"`) |
//! | [`base64_bytes`]| `Vec<u8>` ↔ Base64 string (standard / URL-safe) |
//! | [`timestamp`] | `DateTime<Utc>` from epoch or ISO 8601, as RFC 3339 |
//! | [`maybe_string`]| String-or-number coerced to a target type |