Workflow for allowing the user to avoid repeated authorizations with a spending limit

[dafacto]

There's a problem that would be nice to solve, if we can find an elegant way to solve it:

1. It's annoying and costly for a user to have to repeatedly authorize the token spend prior to transfer.
2. Setting an infinite spending limit exposes the user to smart contract risk

Curve provides an "infinite spend" checkbox, but this isn't ideal, since many users won't understand what it means, and exposes them to maximum risk if they choose to select it. A "reasonable" spending limit would be better, but we really don't want users to have to get into the advanced areas of their wallet.

Here is a possible workflow that might provide an elegant solution. Under the "Allow transfer" button, we show a text link that says, "Don’t ask for authorization again?". Clicking this prompts a modal with:

Avoid future authorizations with a transfer limit

You can save on transaction costs by skipping this authorization step, with a pre-authorizing a transfer limit. For example, if you set a {token} transfer limit of 1,000, you’ll only be required to go through this initial authorization step on transfers above 1,0000 {token}.

Set my {token} pre-authorized transfer limit to:

[       ] {token} 

[Confirm] [Cancel]

(In this case, the Confirm action initiates the the authorization transaction, while setting the future user-specified spending limit.)