Query RelayHub for recipient balance

[frangio]

Fixes the following issue that is part of #1:

the dapp tool assumes that the recipient implements a getRecipientBalance method, which may not always be the case.

I implemented this using the GraphQL stuff that is available in the project.

[asselstine]

Hi @frangio! I missed you at EthBerlin.

I think you could optimize the PR if you replaced recipientQuery in the RecipientForm with your recipientBalanceQuery. The only thing we needed from recipientQuery was the balance, which is no longer used. We can get relayHubAddress from the props. Saves some calls. The RecipientBalance component looks good, but I don't think it's needed here.

[frangio]

We can get relayHubAddress from the props.

From what I see, the only way it's available in the props right now is as a result of the recipientQuery. The indirection is necessary because we need to ask the recipient what RelayHub it's using.

Am I getting this right?

[asselstine]

Yes! My mistake, in the wee hours I was seeing your component props as the RecipientForm props.

So: your component makes sense! The only thing I'd additionally do then is to remove the balance: getRecipientBalance from the recipientQuery if no one else is using it. May as well remove the dead code.

[frangio]

Done.

Should we also add the subscription logic to RecipientBalance? I suppose this is what refreshes the information periodically?

https://github.com/OpenZeppelin/gsn-site/blob/96d7168e61c0bd909ef389342c228241d51bcc85/lib/components/RecipientForm.jsx#L69-L82

[asselstine]

Yup; that's what keeps the data fresh! If you add a corresponding snippet it will be updated in realtime.

[frangio]

Cool. It should be ready now.

[frangio]

Thanks for reviewing @asselstine!