[#3] Implements Base64URL encode / decode

src/main/java/io/github/raeperd/realworld/infrastructure/jwt/Base64URL.java

@@ -0,0 +1,20 @@
+package io.github.raeperd.realworld.infrastructure.jwt;
+
+import java.nio.charset.StandardCharsets;
+import java.util.Base64;
+
+class Base64URL {
+
+    private Base64URL() {
+    }
+
+    static String base64URLFromString(String rawString) {
+        return Base64.getUrlEncoder().withoutPadding()
+                .encodeToString(rawString.getBytes(StandardCharsets.UTF_8));
+    }
+
+    static String stringFromBase64URL(String base64URL) {
+        return new String(Base64.getUrlDecoder().decode(base64URL));
+    }
+
+}

src/test/java/io/github/raeperd/realworld/infrastructure/jwt/Base64URLTest.java

@@ -0,0 +1,40 @@
+package io.github.raeperd.realworld.infrastructure.jwt;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Random;
+
+import static io.github.raeperd.realworld.infrastructure.jwt.Base64URL.base64URLFromString;
+import static io.github.raeperd.realworld.infrastructure.jwt.Base64URL.stringFromBase64URL;
+import static org.assertj.core.api.Assertions.assertThat;
+
+class Base64URLTest {
+
+    private final static String RAW_STRING = "something";
+    private final static String ENCODED_STRING = "c29tZXRoaW5n";
+
+    @Test
+    void when_encode_return_expected_string() {
+        assertThat(base64URLFromString(RAW_STRING)).isEqualTo(ENCODED_STRING);
+    }
+
+    @Test
+    void when_decode_return_expected_string() {
+        assertThat(stringFromBase64URL(ENCODED_STRING)).isEqualTo(RAW_STRING);
+    }
+
+    @Test
+    void when_encode_and_then_decode_expect_same() {
+        final var rawString = generateRandomString();
+
+        final var encodedString = base64URLFromString(rawString);
+        assertThat(stringFromBase64URL(encodedString)).isEqualTo(rawString);
+    }
+
+    private String generateRandomString() {
+        final var bytes = new byte[7];
+        new Random().nextBytes(bytes);
+        return new String(bytes);
+    }
+
+}