Restore R2DBC MySQL support with Spring Boot 3.1 or later

`io.asyncer:r2dbc-mysql` was added in the dependency management
in spring boot 3.1. Currently, when r2dbc and mysql are selected
the generated project doesn't include the new dependency. This
commit fixes the behavior.

See gh-1285

start-site/src/main/java/io/spring/start/site/extension/dependency/springdata/R2dbcBuildCustomizer.java

@@ -38,6 +38,7 @@
  * @author Stephane Nicoll
  * @author Andy Wilkinson
  * @author Brian Clozel
+ * @author Eddú Meléndez
  */
 public class R2dbcBuildCustomizer implements BuildCustomizer<Build> {
 
@@ -47,16 +48,21 @@ public class R2dbcBuildCustomizer implements BuildCustomizer<Build> {
 
 	private static final VersionRange SPRING_BOOT_3_0_0_OR_LATER = VersionParser.DEFAULT.parseRange("3.0.0-M1");
 
+	private static final VersionRange SPRING_BOOT_3_1_0_OR_LATER = VersionParser.DEFAULT.parseRange("3.1.0");
+
 	private final boolean borcaOrLater;
 
 	private final boolean mariaDbIsUnmanaged;
 
 	private final boolean sqlServerIsUnmanaged;
 
+	private final boolean mysqlR2dbcNewDependency;
+
 	public R2dbcBuildCustomizer(Version platformVersion) {
 		this.borcaOrLater = SPRING_BOOT_2_7_0_OR_LATER.match(platformVersion);
 		this.mariaDbIsUnmanaged = SPRING_BOOT_3_0_0_OR_LATER.match(platformVersion);
 		this.sqlServerIsUnmanaged = SPRING_BOOT_3_0_0_OR_LATER.match(platformVersion);
+		this.mysqlR2dbcNewDependency = SPRING_BOOT_3_1_0_OR_LATER.match(platformVersion);
 	}
 
 	@Override
@@ -71,6 +77,9 @@ public void customize(Build build) {
 		if (build.dependencies().has("mysql") && !this.borcaOrLater) {
 			addManagedDriver(build.dependencies(), "dev.miku", "r2dbc-mysql");
 		}
+		if (build.dependencies().has("mysql") && this.mysqlR2dbcNewDependency) {
+			addManagedDriver(build.dependencies(), "io.asyncer", "r2dbc-mysql");
+		}
 		if (build.dependencies().has("postgresql")) {
 			String groupId = this.borcaOrLater ? "org.postgresql" : "io.r2dbc";
 			addManagedDriver(build.dependencies(), groupId, "r2dbc-postgresql");

start-site/src/test/java/io/spring/start/site/extension/dependency/springdata/R2dbcBuildCustomizerTests.java

@@ -33,6 +33,7 @@
  * Tests for {@link R2dbcBuildCustomizer}.
  *
  * @author Stephane Nicoll
+ * @author Eddú Meléndez
  */
 class R2dbcBuildCustomizerTests extends AbstractExtensionTests {
 
@@ -72,6 +73,7 @@ void r2dbcWithMysql() {
 		build.dependencies().add("mysql");
 		customize(build, Version.parse("2.6.8"));
 		assertThat(build.dependencies().ids()).containsOnly("data-r2dbc", "mysql", "r2dbc-mysql");
+		assertThat(build.dependencies().get("r2dbc-mysql").getGroupId()).isEqualTo("dev.miku");
 	}
 
 	@Test
@@ -83,6 +85,16 @@ void r2dbcWithMysqlAndBorca() {
 		assertThat(build.dependencies().ids()).containsOnly("data-r2dbc", "mysql");
 	}
 
+	@Test
+	void r2dbcWithMysqlAndSpringBoot31() {
+		Build build = createBuild();
+		build.dependencies().add("data-r2dbc");
+		build.dependencies().add("mysql");
+		customize(build, Version.parse("3.1.0"));
+		assertThat(build.dependencies().ids()).containsOnly("data-r2dbc", "mysql", "r2dbc-mysql");
+		assertThat(build.dependencies().get("r2dbc-mysql").getGroupId()).isEqualTo("io.asyncer");
+	}
+
 	@Test
 	void r2dbcWithPostgresql() {
 		Build build = createBuild();