Deposit to and withdraw from UDC

[manuelwedler]

Is your feature request related to a problem? Please describe.

There should be a way to deposit to the UDC directly from the WebUI. Having the withdraw functionality would also be nice.

Describe the solution you'd like

There could be button close to the UDC balance in the header which opens a pop up for managing the UDC funds. In the pop up the user could deposit and withdraw.

Triggering the transaction

There are two options for the deposit:

1. The deposit transaction could be done from the raiden client and the account it controls. This would need a new API call. (API endpoint for UDC contract to deposit and withdraw RDN tokens  raiden#5497)
2. It could also be done via MetaMask from a different account.

The withdraw can't be done on the behalf of another account. So for it only an API call is possible with the current version of the contracts.

[czepluch]

I would love to see this being prioritized. We often get questions about how to deposit to the UDC!

[manuelwedler]

We decided to have the respective API calls in the client (raiden-network/raiden#5497) and not use MetaMask. The reasion is we would need it any way for the withdraw and do not have any transactions triggered by MetaMask yet and want to continue like this for consistency.

[sashseurat]

Draft with quick click-dummy is here:
https://www.figma.com/proto/Q5sJRXwMH3ydOTzQlchO0T/WebUI-UDC-Management-UXUI?node-id=511%3A496&viewport=-33%2C716%2C0.12004529684782028&scaling=scale-down

Also reviewed with Manuel