incorrect examples for paying AMP invoices

[ZZiigguurraatt]

At

docs.lightning.engineering/lightning-network-tools/lnd/amp.md

Line 79 in 0ba7c3c

If your mobile wallet supports payments to AMP invoices, the invoice needs to be scanned and optionally the amount needs to be specified. To pay an AMP invoice from the command line, you only need to execute `lncli payinvoice <amp invoice>` If the AMP invoice does not contain an amount, you can specify the amount you would like to pay with the `--amt` flag.

it says to use lncli payinvoice <amp invoice> to pay an AMP invoice.

However, that results in

[lncli] rpc error: code = Unknown desc = the AMP flag (--amp or SendPaymentRequest.Amp) must be set to pay an AMP invoice

because the --amp flag is not included.

Also,

docs.lightning.engineering/lightning-network-tools/lnd/amp.md

Line 63 in 0ba7c3c

`lncli payinvoice --pay_req <the amp invoice created by the receiver> --amp-reuse`

suggests using a --amp-reuse flag, but that is wrong and does not exist.

Also

docs.lightning.engineering/lightning-network-tools/lnd/amp.md

Line 57 in 0ba7c3c

`lncli payinvoice --pay_req <the amp invoice created by the receiver>`

and

docs.lightning.engineering/lightning-network-tools/lnd/amp.md

Line 61 in 0ba7c3c

`lncli payinvoice --pay_req <the amp invoice created by the receiver> --pay_addr <the sha256 hash of a random number>`

are missing the --amp flag as well.

Also, some places payinvoice is used and some places sendpayment is used on this page. Seems like mixing and matching those two causes a little confusion. It is also redundant to include --pay_req= with the payinvoice command since payinvoice is shorthand for sendpayment --pay_req=.

[ZZiigguurraatt]

While editing this page, it also might be nice to add an example of what an AMP invoice looks like. I was not aware until today that an AMP invoice was embedded inside what looks like a BOLT 11 invoice. I'm not sure how this is possible, so it might be nice to reference where in the BOLT11 spec this is possible, and if that is from a bLIP or what.