Add ConsentVersion value object

This represents the consent type at hand (implicit or explicit consent).
A third option is that no consent has been given.

src/OpenConext/EngineBlock/Authentication/Value/ConsentVersion.php

@@ -0,0 +1,77 @@
+<?php
+
+/**
+ * Copyright 2010 SURFnet B.V.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+namespace OpenConext\EngineBlock\Authentication\Value;
+
+use OpenConext\EngineBlock\Assert\Assertion;
+
+final class ConsentVersion
+{
+    const STABLE = 'stable';
+    const UNSTABLE = 'unstable';
+    const NOT_GIVEN = 'not-given';
+
+    /**
+     * @var string
+     */
+    private $consentVersion;
+
+    public static function stable(): ConsentVersion
+    {
+        return new self(self::STABLE);
+    }
+
+    public static function unstable(): ConsentVersion
+    {
+        return new self(self::UNSTABLE);
+    }
+
+    public static function notGiven(): ConsentVersion
+    {
+        return new self(self::NOT_GIVEN);
+    }
+
+    public function __construct(string $consentVersion)
+    {
+        Assertion::choice(
+            $consentVersion,
+            [self::UNSTABLE, self::STABLE, self::NOT_GIVEN],
+            'ConsentVersion must be one of ConsentVersion::STABLE, ConsentVersion::NOT_GIVEN or ConsentVersion::UNSTABLE'
+        );
+
+        $this->consentVersion = $consentVersion;
+    }
+
+    public function given(): bool
+    {
+        return $this->consentVersion !== self::NOT_GIVEN;
+    }
+
+    /**
+     * @return string
+     */
+    public function __toString()
+    {
+        return $this->consentVersion;
+    }
+
+    public function isUnstable(): bool
+    {
+        return $this->consentVersion === self::UNSTABLE;
+    }
+}