GPU: Allow a farmer to set a custom "extra" price on a node in the dashboard

[DylanVerstraete]

To complete threefoldtech/home#1392 we need on chain a way to set an extra price. But we also need a flow in the dashboard for a farmer to set a custom price.

I would suggest adding the new "button" on the farmer's node overview page where a modal opens so he can view/set an extra price.

A call to tfchain smartContractModule.setDedicatedNodeExtraFee must be mode with (node_id: u32, extra_fee: u64).

The extra_fee is expressed in mUSD (milli usd => USD * 1000)

Errors will be thrown when:

• the node has active deployments
• the node is rented already

[AhmedHanafy725]

for these errors, does it mean that the farmer can't set the extra fee if the node has node/rent contracts?

[DylanVerstraete]

he farmer can't set the extra fee if the node has node/rent contracts

Yes indeed

[renauter]

See some specs from TFChain side here:
threefoldtech/tfchain#725

[A-Harby]

Verified.