Currency Rate Update: Croatia-HNB

This module plugs the Croatian National Bank (HNB) into Odoo's currency rate update system. Once installed, a new provider option called "Croatia-HNB" becomes available wherever exchange rate providers are configured (the currency rate provider settings that come from the base currency rate update module).

When a provider is set to Croatia-HNB, Odoo contacts the HNB public web service to fetch official rates. Users can:

• Choose which currencies to update; the module asks HNB which currencies it supports and only keeps rates for the currencies selected on the provider.
• Fetch rates for a date range, so historical rates can be loaded, not just today's.
• Pick which HNB rate type to use. A system setting stores the rate type, defaulting to "srednji" (the middle/reference rate). The chosen type is used when reading the downloaded data.

Rates are returned per application date and stored as currency rates, so they feed into Odoo's normal currency conversion for accounting, sales and purchases. The module only extends the existing rate provider model (res.currency.rate.provider) and adds one configuration parameter; it does not create new menus or screens of its own. If the HNB response contains a value that cannot be read as a number, that entry is skipped and logged instead of breaking the whole update.