Remove Norway rate but add an option to add it back again

See these as why NO was removed:
driesvints#43
driesvints#14 (comment)

README.md

@@ -34,6 +34,7 @@ $vatCalculator->isValidVatNumber('NL123456789B01');
 	- [Validate EU VAT numbers](#validate-eu-vat-numbers)
 	- [Get EU VAT number details](#vat-number-details)
 	- [Get the IP based country of your user](#get-ip-based-country)
+	- [Countries](#countries)
 - [License](#license)
 
 <a name="installation"></a>
@@ -143,6 +144,17 @@ try {
 }
 ```
 
+<a name="countries"></a>
+## Countries
+
+EU countries are supported as well as some non-EU countries that use VAT. Some countries are not supported even though they also have VAT. Currently, that's the case for Norway which can be added manually with `VatRates::addRateForCountry()`.
+
+```php
+$vatRates = new VatRates();
+$vatRates->addRateForCountry('NO');
+$vatCalculator = new VatCalculator($vatRates);
+```
+
 <a name="license"></a>
 ## License
 This library is licensed under the MIT license. Please see [License file](LICENSE.md) for more information.

UPGRADE.md

@@ -5,6 +5,7 @@
 * Exceptions (`VatCheckUnavailableException`) are always thrown, `forwardSoapFaults` option has been removed (**BC BREAK**)
 * Some countries have various VAT rates depending on location resulting in `getTaxRateForCountry()` removal, use `getTaxRateForLocation()` instead (**BC BREAK**)
 * Rates have been moved to a separate class `VatRates`, you need to pass the class to `VatCalculator` constructor  (**BC BREAK**)
+* Norway VAT rate removed, can be manually added back with `VatRates::addRateForCountry()`
 * `getIPBasedCountry()` & `getClientIP()` methods have been removed, use some other package (or `CF-IPCountry` HTTP header if you're behind Cloudflare)
 * Some methods have been properly *camelCased*: methods like `getClientIP()` -> `getClientIp()` and `shouldCollectVAT` -> `shouldCollectVat` and a few more
 * `VATCheckUnavailableException` has been *camelCased* to `VatCheckUnavailableException`

src/VatRates.php

@@ -176,6 +176,16 @@ class VatRates
 		'TR' => [ // Turkey
 			'rate' => 0.18,
 		],
+	];
+
+	/**
+	 * Optional tax rules.
+	 *
+	 * These are added manually by `addRateForCountry()`
+	 *
+	 * @var array<string, array>
+	 */
+	private $optionalTaxRules = [
 		'NO' => [ // Norway
 			'rate' => 0.25,
 		],
@@ -332,6 +342,13 @@ class VatRates
 	];
 
 
+	public function addRateForCountry(string $country): void
+	{
+		$country = strtoupper($country);
+		$this->taxRules[$country] = $this->optionalTaxRules[$country] ?? null;
+	}
+
+
 	public function shouldCollectVat(string $countryCode): bool
 	{
 		return isset($this->taxRules[strtoupper($countryCode)]);

tests/VatRatesTest.php

@@ -0,0 +1,42 @@
+<?php
+declare(strict_types = 1);
+
+namespace Spaze\VatCalculator;
+
+use PHPUnit_Framework_TestCase;
+
+class VatRatesTest extends PHPUnit_Framework_TestCase
+{
+
+	/** @var VatRates */
+	private $vatRates;
+
+
+	protected function setUp()
+	{
+		$this->vatRates = new VatRates();
+	}
+
+
+	public function testAddRateKnownCountry(): void
+	{
+		$country = 'nO';
+		$this->assertFalse($this->vatRates->shouldCollectVat($country));
+		$this->assertEquals(0, $this->vatRates->getTaxRateForLocation($country));
+		$this->vatRates->addRateForCountry($country);
+		$this->assertTrue($this->vatRates->shouldCollectVat($country));
+		$this->assertEquals(0.25, $this->vatRates->getTaxRateForLocation($country));
+	}
+
+
+	public function testAddRateUnknownCountry(): void
+	{
+		$country = 'yEs';
+		$this->assertFalse($this->vatRates->shouldCollectVat($country));
+		$this->assertEquals(0, $this->vatRates->getTaxRateForLocation($country));
+		$this->vatRates->addRateForCountry($country);
+		$this->assertFalse($this->vatRates->shouldCollectVat($country));
+		$this->assertEquals(0, $this->vatRates->getTaxRateForLocation($country));
+	}
+
+}