Add tax treatment classification for investment accounts with international support (#693)

* Add tax treatment support for accounts, investments, and cryptos

* Replace hardcoded region labels with I18n translations

* Add I18n support for subtype labels with fallback to hardcoded values

* fixed schema

---------

Co-authored-by: luckyPipewrench <luckypipewrench@proton.me>

test/models/crypto_test.rb

@@ -0,0 +1,30 @@
+require "test_helper"
+
+class CryptoTest < ActiveSupport::TestCase
+  test "tax_treatment defaults to taxable" do
+    crypto = Crypto.new
+    assert_equal "taxable", crypto.tax_treatment
+  end
+
+  test "tax_treatment can be set to tax_deferred" do
+    crypto = Crypto.new(tax_treatment: :tax_deferred)
+    assert_equal "tax_deferred", crypto.tax_treatment
+  end
+
+  test "tax_treatment can be set to tax_exempt" do
+    crypto = Crypto.new(tax_treatment: :tax_exempt)
+    assert_equal "tax_exempt", crypto.tax_treatment
+  end
+
+  test "tax_treatment enum provides predicate methods" do
+    crypto = Crypto.new(tax_treatment: :taxable)
+    assert crypto.taxable?
+    assert_not crypto.tax_deferred?
+    assert_not crypto.tax_exempt?
+
+    crypto.tax_treatment = :tax_deferred
+    assert_not crypto.taxable?
+    assert crypto.tax_deferred?
+    assert_not crypto.tax_exempt?
+  end
+end