Include the warning about low ether balance in the webui.

[rakanalh]

Abstract

The UI should warn the user when the ether balance is less than a certain threshold to be able to pay the gas costs of future transactions.

Motivation

Warnings should be more visible to enable the user to react on time about them and resolve them to avoid any disruption of service / issues in running a node.

Related to

https://github.com/raiden-network/webui/issues/192

[LefterisJP]

Note: Does not need to only be warnings. Can be any kind of messages that need to be seen by the user.

[ulope]

I can't find the issue but we discussed this at some point in the past.

One proposal was to change the API response to always have a predefined structure that on the one hand contains the actual response to the API call and an additional field or structure that contains messages, warnings, stats, etc.