Offer an option to create a higher approval for investing and insuring

[christoph2806]

Currently, you are asked to approve token transfers each time you purchase a policy or fund a riskpool.
In DeFi it's pretty standard to give a high approval one time and use it many times afterwards.
This comes at a certain risk because in case of a smart contract exploit, users funds would be at risk.
Therefore I propose the following implementation:

1. The current approval is displayed somewhere on the page. If the approval is higher than the current token balance, the balance is displayed in warning color or with a warning hint.
2. Each time the user is asked for approval, a dialog offers the following three options:
   • Approve only the amount necessary for the next transaction
   • Approve the full current token balance
   • Approve an infinite amount, ie. maxInt

The user can select one of the options and then the approval is processed.

[doerfli]

This should also be done for the staking-ui

[gebunu]

agree with @doerfli this also happens in staking-ui