frontend: disable transfer creation if not enough liquidity available

[manuelwedler]

Issue Desription

We would like to disable the transfer submit button in case the transfer cannot get filled due to liquidity. We should check the token balance of all agents on the target chain and disable if none of them has enough tokens for fulfillment. For this a new validator function needs to be implemented and integrated into the form.

Acceptance Criteria

• [ ] check the token balances of the agents for the selected token on the target chain
• [ ] disable transfer button in case no agent has as much tokens as the user's input in the amount field

[manuelwedler]

Hey team! Please add your planning poker estimate with Zenhub @bilbeyt @istankovic @fredo

[fredo]

how are the agent addresses retrieved?

[manuelwedler]

I thought I could get them from the RequestManager contract but just realized that it is implemented as mapping it is not trivial to get them from the chain.

Daniel proposed to hardcode them. Would you be fine with that? @fredo

[fredo]

for the beginning yes

[fredo]

as a second step we could get it from the subgraph?

[manuelwedler]

Sounds good to me :+1: