feat(module/mariadb): Add getR2dbcUrl() to MariaDBR2DBCDatabaseContainer

This adds a static helper method `getR2dbcUrl(MariaDBContainer)` to generate a valid R2DBC connection string. This simplifies configuration for R2DBC users.

Relates to #8797

Author: taole33

modules/mariadb/src/main/java/org/testcontainers/containers/MariaDBR2DBCDatabaseContainer.java

@@ -32,4 +32,15 @@ public ConnectionFactoryOptions configure(ConnectionFactoryOptions options) {
             .option(ConnectionFactoryOptions.PASSWORD, container.getPassword())
             .build();
     }
+
+    public static String getR2dbcUrl(MariaDBContainer<?> container) {
+        return String.format(
+            "r2dbc:mariadb://%s:%s@%s:%d/%s",
+            container.getUsername(),
+            container.getPassword(),
+            container.getHost(),
+            container.getMappedPort(MariaDBContainer.MARIADB_PORT),
+            container.getDatabaseName()
+        );
+    }
 }

modules/mariadb/src/test/java/org/testcontainers/containers/MariaDBR2DBCDatabaseContainerTest.java

@@ -1,9 +1,13 @@
 package org.testcontainers.containers;
 
 import io.r2dbc.spi.ConnectionFactoryOptions;
+import org.junit.jupiter.api.Test;
+import org.testcontainers.MariaDBTestImages;
 import org.testcontainers.r2dbc.AbstractR2DBCDatabaseContainerTest;
 import org.testcontainers.utility.DockerImageName;
 
+import static org.assertj.core.api.Assertions.assertThat;
+
 public class MariaDBR2DBCDatabaseContainerTest extends AbstractR2DBCDatabaseContainerTest<MariaDBContainer<?>> {
 
     @Override
@@ -20,4 +24,25 @@ protected String createR2DBCUrl() {
     protected MariaDBContainer<?> createContainer() {
         return new MariaDBContainer<>(DockerImageName.parse("mariadb:10.3.39"));
     }
+
+    @Test
+    public void testGetR2dbcUrl() {
+        try (MariaDBContainer<?> container = new MariaDBContainer<>(MariaDBTestImages.MARIADB_IMAGE)) {
+            container.start();
+
+            String r2dbcUrl = MariaDBR2DBCDatabaseContainer.getR2dbcUrl(container);
+
+            String user = container.getUsername();
+            String password = container.getPassword();
+            String host = container.getHost();
+            Integer port = container.getMappedPort(MariaDBContainer.MARIADB_PORT);
+            String db = container.getDatabaseName();
+
+            String expectedPattern = String.format("^r2dbc:mariadb://%s:%s@%s:%d/%s$", user, password, host, port, db);
+
+            assertThat(r2dbcUrl)
+                .as("URL must strictly match format 'r2dbc:mariadb://user:pass@host:port/db'")
+                .matches(expectedPattern);
+        }
+    }
 }