Polishing: Lookup FX rate in currency table on foreign currency transactions

[ehuelsmann]

When the user selects a foreign currency transaction in one of the following screens, an input box with an exchange rate appears. To polish our UX, we should be pre-filling the FX rate with the rate specific to the indicated currency as applicable to the transaction date which is in the table of (advisory) FX rates. [note that this is just a proposal and any changes by the user to that rate are to be respected!].

• [ ] AR/AP transaction screen
• [ ] AR/AP transaction payments rows
• [ ] Sales/Purchase invoice screen
• [ ] Sales/Purchase invoice payment rows
• [ ] GL transaction screen
• [ ] (Bulk) Payment screen

(Note that this list was compiled top-of-mind and is to be completed before work on this issue is started.)

[sbts]

When implementing this, we probably should include a "refresh rate" button and an onchange event to refresh the rate when the date field changes.

The refresh rate button should always work to grab the date relevant rate. It should also "clear" the manual rate flag if it's set

The onchange update should only be effective if a manual rate HAS NOT been entered