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Bug Fix

Contacts: is_on_whatsapp and get_user_info compile in #[async_trait] contexts (#826) Calling either method from an #[async_trait] implementation — or any other context that boxes the returned future — previously produced a hard compiler error: 
error: implementation of `FnOnce` is not general enough
  = note: closure with signature `fn(&'0 IsOnWhatsAppResult) -> (&Jid, Option<&Jid>)`
          must implement `FnOnce<(&'1 IsOnWhatsAppResult,)>`, for any two lifetimes `'0` and `'1`...
The root cause was inside the library: the internal persist_lid_mappings helper received closures that returned references tied to a concrete lifetime. Rust infers such closures at a single lifetime rather than the higher-ranked for<'r> Fn(&'r _) form. Because the closure types were embedded in the public methods’ future types, the unprovable HRTB obligation leaked to every boxing consumer — nothing in user code could work around it. Fix. The three offending closures are now named fn items (forward_lid_pair, reverse_lid_pair, user_info_lid_pair), which implement Fn for every lifetime by construction. No API changes, no extra allocations, identical behavior. A compile-time regression guard (tests/async_trait_boxed_future_compat.rs) was added that reproduces the exact consumer shape from the original report — an #[async_trait] impl holding an RwLock<Option<Arc<Client>>> — and fails to compile if the issue is ever reintroduced. No breaking changes. Fixes #825.