Multi-currency support (#425)

* Initial foundational pass at multi-currency

* Default format currency

* More work on currency and exchanging

* Re-build currencies on change

* Currency import/setup

* Background job overhaul + cheaper OXR plan support

* Lint fixes

* Test fixes

* Multi-currency setup instructions

* Allow decimals in the balance field

* Spacing fix for form

---------

Signed-off-by: Josh Pigford <josh@joshpigford.com>

app/views/settings/edit.html.erb

@@ -3,6 +3,8 @@
 <%= form_with model: Current.user, url: settings_path, html: { class: "space-y-4" } do |form| %>
   <%= form.fields_for :family_attributes do |family_fields| %>
     <%= family_fields.text_field :name, placeholder: "Family name", value: Current.family.name, label: "Family name" %>
+
+    <%= family_fields.select :currency, options_for_select(Currency.all.order(iso_code: :asc).map { |currency| ["#{currency.iso_code} (#{currency.name})", currency.iso_code] }, selected: Current.family.currency), { label: "Currency" } %>
   <% end %>
 
   <%= form.text_field :first_name, placeholder: "First name", value: Current.user.first_name, label: true %>