Function resolve_callback 

pub async fn resolve_callback(
    pool: &PgPool,
    callback_id: Uuid,
    payload: Option<Value>,
    default_action: DefaultAction,
    run_lease: Option<i64>,
) -> Result<ResolveOutcome, AwaError>

Resolve a callback by evaluating CEL expressions against the payload.

Uses a transaction with SELECT ... FOR UPDATE for atomicity. The default_action determines behaviour when no CEL conditions match or no expressions are configured.