feat: check if coin already in cache

[hal3e]

Summary

Checks if any of the inputs is already cached before sending/submitting the tx.

[MujkicA]

IIRC the plus here is that we prevent the user from hitting the network with a tx that's bound to fail, which is great.

I have two concerns, correct me if I'm wrong:

• We might get inconsistent results because of the time based eviction. E.g. user stalls submitting the second transaction long enough for the cache to drop the entry.
• We don't evict when txs are dropped by the node which means we might prevent the user from executing a valid transaction at some point.

[MujkicA]

If the user lacks some context on how the cache or UTXO based systems work, this message might not be enough.

Saying something like:

"a transaction with this input was submitted recently, attempting to spend it again will result in an error".

should give a better idea of what the issue is.

[hal3e]

IIRC the plus here is that we prevent the user from hitting the network with a tx that's bound to fail, which is great.

I have two concerns, correct me if I'm wrong:

* We might get inconsistent results because of the time based eviction. E.g. user stalls submitting the second transaction long enough for the cache to drop the entry.

* We don't evict when txs are dropped by the node which means we might prevent the user from executing a valid transaction at some point.

• If the cache drops the entry because of time based eviction then we revert to the old behavior. We send the the tx and the node will complain.
• This can also happen with the current implementation; however, only if the tx is squeezed out.

^ Had meeting with @segfault-magnet and @MujkicA where we went through the uses cases and we came to the above conclusions.