Sellers payment API. - Githubissues

Sellers should be able to process Gooddollar payments through our API.

A Seller like e-commerce for "brand" would like to be able to request payment from his customers at Gooddollar.

Create a typescript NPM module that works both on browser/node that implements the following methods

[ ] generatePaymentLink(PaymentDetails):string
- Similar to (https://github.com/GoodDollar/GoodDAPP/blob/master/src/lib/share/index.js generateCode + readCode)
- Should include extra details from PaymentDetails
  
  Example:
  
  http://wallet.gooddollar.org:3000/? code=eyJtIjoiM2RQQjRxUjNBZUoyY0tzalJnYWp3dE1hUms3TjI0aFVMZzYiLCJhIjoiM... the query param code is the base64 encrypted value returned from generateCode
The generated code should return an object with the paymenDetails params and the ones that we already have

Example:
```
{
    "m":"3dPB4qR3AeJ2cKsjRgajwtMaRk7N24hULg6",
    "a":"22200",
    "r":"afds",
    "cat":"Digital Services"
}
```
[ ] generatePaymentQR(PaymentDetails):image
- Same as above but create a QR containing the payment link from the generatePaymentLink method described above. I suggest https://www.npmjs.com/package/qrcode for generating the image
[ ] validateTx(TxData):boolean
- Reads fuse blockchain for txhash and check it has a Transfer log with the amount + sha3(invoiceid/data) paid to recipient in event log data
[ ] async onPayment(recipient,invoiceid):Promise
- Listens to Transfer event with to=recipient and data=sha3(invoiceid/data)
- resolves promise once event detected
  Types
```
PaymentDetails: {
recipient,
amount,
reason,
category,
invoiceId,
data?,
sellerName?,
sellerWebsite?,
callbackurl
}
```

TxData: { txHash, recipient, amount invoiceId, data? }



### To get approved or help join: 
 https://t.me/gooddollarbounties

 #### Also for any questions refer to: 
 @TomasGonzalez

GoodDollar / Bounties