Update hard-coded currency UI with currency specific params (#488)

* Update hard-coded currency UI with currency specific params

* Rename extension methods to match currency option names; Move cents extension to numeric class extension

* Use currency's precision to show the cents part in accounts show page

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Co-authored-by: Sriram Krishnan <sriram@seafoodsouq.com>

test/initializers/numeric_extensions_test.rb

@@ -0,0 +1,28 @@
+# test/initializers/big_decimal_extensions_test.rb
+require "test_helper"
+
+class NumericExtensionsTest < ActiveSupport::TestCase
+  test "#cents returns the cents part with 2 precisions by default" do
+    amount = 123.45
+    assert_equal "45", amount.cents
+  end
+
+  test "#cents returns empty when precision is 0" do
+    amount = 123.45
+    assert_equal "", amount.cents(precision: 0)
+  end
+
+  test "#cents returns the cents part of the string with given precision" do
+    amount = 123.4862
+    assert_equal "4", amount.cents(precision: 1)
+    assert_equal "486", amount.cents(precision: 3)
+  end
+
+  test "#cents pads the cents part with zeros up to the specified precision" do
+    amount_without_decimal = 123
+    amount_with_decimal = 123.4
+
+    assert_equal "00", amount_without_decimal.cents
+    assert_equal "40", amount_with_decimal.cents
+  end
+end

test/initializers/string_extensions_test.rb

@@ -0,0 +1,19 @@
+# test/string_extensions_test.rb
+require "test_helper"
+
+class StringExtensionsTest < ActiveSupport::TestCase
+  test "#unit returns the currency unit for a given currency code" do
+    assert_equal "$", "USD".unit
+    assert_equal "€", "EUR".unit
+  end
+
+  test "#separator returns the currency separator for a given currency code" do
+    assert_equal ".", "USD".separator
+    assert_equal ",", "EUR".separator
+  end
+
+  test "#precision returns the currency's precision for a given currency code" do
+    assert_equal 2, "USD".precision
+    assert_equal 0, "KRW".precision
+  end
+end