Lot price must be amount to be compatible with Ledger

[xkikeg]

Currently my program accepts the one below

2023/4/20 stock
    Assets:Brokers                               -10 FOOBAR {(1000.00/10 USD)} @ 110 USD
    Income:Capital Gain                         -100 USD
    Assets:Banks                               1,100 USD

But Ledger doesn't accept this.

While parsing posting:
  Assets:Brokers                               -10 FOOBAR {(1000.00/10 USD)} @ 110 USD
                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Error: No quantity specified for amount

OTOH, if you remove the parens, Ledger still ignores the expression silently.

> 2023/4/20 stock
>     Assets:Brokers                               -10 FOOBAR {1000.00/10 USD} @ 110 USD
>     Income:Capital Gain                         -100 USD
>     Assets:Banks                               1,100 USD
Unbalanced remainder is:
         -100.00 USD
Amount to balance against:
        1,100.00 USD

So probably we should

• Make lot price bare amount only, and clearly states expression isn't supported yet
• (In future, if possible) support expression as a lot price with optional feature guard.