Function update_admin 

pub fn update_admin<K>(env: &Env, admin_key: &K, new_admin: &Address)
where
    K: IntoVal<Env, Val> + TryFromVal<Env, Val> + Clone,

Update the contract administrator

Changes the admin address to a new address. Only the current admin can call this function.

Arguments

• env - The Soroban environment
• admin_key - Storage key for the admin address (e.g., DataKey::Admin)
• new_admin - Address of the new administrator

Panics

Panics if the caller is not the current admin