Use browser's locale for currency format

app/helpers/fmt-fiat-currency.js

@@ -1,10 +1,11 @@
 import { helper } from '@ember/component/helper';
 
 export default helper(function fmtFiatCurrency(params) {
-  const formatter = new Intl.NumberFormat('en-US', {
+  const lang = navigator.language || navigator.userLanguage;
+  const formatter = new Intl.NumberFormat(lang, {
     style: 'currency',
     currency: params[1] || 'EUR',
-    minimumFractionDigits: 2
+    currencyDisplay: 'code'
   })
   return formatter.format(params[0]);
 });

tests/integration/helpers/fmt-fiat-currency-test.js

@@ -10,9 +10,13 @@ module('Integration | Helper | fmt-fiat-currency', function(hooks) {
     this.set('amount', 13.9);
 
     await render(hbs`{{fmt-fiat-currency this.amount}}`);
-    assert.equal(this.element.textContent.trim(), '€13.90', 'using EUR amount by default');
+    assert.ok(this.element.textContent.trim().match(/13.90/),
+              'formats the number with two decimals');
+    assert.ok(this.element.textContent.trim().match(/EUR/),
+              'using EUR by default');
 
     await render(hbs`{{fmt-fiat-currency this.amount 'USD'}}`);
-    assert.equal(this.element.textContent.trim(), '$13.90', 'using the defined currency');
+    assert.ok(this.element.textContent.trim().match(/USD/),
+              'using defined currency when given');
   });
 });