Function select_token_utxos 

pub fn select_token_utxos(
    utxos: &[ChronikUtxo],
    token_id: &str,
    token_amount: u64,
) -> Result<(Vec<ChronikUtxo>, CoinSelection), String>

Select UTXOs that contain a specific SLP/ALP token. Returns the token UTXOs + plain XEC UTXOs needed to cover the fee.