title: R2DBC unable to create connection with h2 protocol
body: <p>I'm trying to leverage H2 for testing and have the following configuration in <code>src/test/resources/application.yaml</code>:</p>
  
  <pre><code>spring:
    r2dbc:
      url: r2dbc:h2:file://testdb
  </code></pre>
  
  <p>I have an empty test annotated with <code>@SpringBootTest</code> but when I run it I get the following error:</p>
  
  <pre><code>Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [io.r2dbc.pool.ConnectionPool]: Factory method 'connectionFactory' threw exception; nested exception is java.lang.IllegalStateException: Unable to create a ConnectionFactory for 'ConnectionFactoryOptions{options={driver=h2, protocol=file, host=testdb}}'. Available drivers: [ pool, postgresql, h2 ]
      at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185)
      at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:651)
      ... 131 common frames omitted
  Caused by: java.lang.IllegalStateException: Unable to create a ConnectionFactory for 'ConnectionFactoryOptions{options={driver=h2, protocol=file, host=testdb}}'. Available drivers: [ pool, postgresql, h2 ]
      at io.r2dbc.spi.ConnectionFactories.get(ConnectionFactories.java:145)
      at org.springframework.boot.autoconfigure.r2dbc.ConnectionFactoryBuilder.build(ConnectionFactoryBuilder.java:125)
      at org.springframework.boot.autoconfigure.r2dbc.ConnectionFactoryConfigurations.createConnectionFactory(ConnectionFactoryConfigurations.java:56)
      at org.springframework.boot.autoconfigure.r2dbc.ConnectionFactoryConfigurations$Pool.connectionFactory(ConnectionFactoryConfigurations.java:68)
      at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
      at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
      at java.base/java.lang.reflect.Method.invoke(Method.java:566)
      at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154)
      ... 132 common frames omitted
  </code></pre>
  
  <p>Here are the relevant dependencies from <code>pom.xml</code>:</p>
  
  <pre><code>&lt;dependency&gt;
      &lt;groupId&gt;io.r2dbc&lt;/groupId&gt;
      &lt;artifactId&gt;r2dbc-h2&lt;/artifactId&gt;
      &lt;version&gt;0.8.4.RELEASE&lt;/version&gt;
      &lt;scope&gt;test&lt;/scope&gt;
  &lt;/dependency&gt;
  &lt;dependency&gt;
      &lt;groupId&gt;com.h2database&lt;/groupId&gt;
      &lt;artifactId&gt;h2&lt;/artifactId&gt;
      &lt;version&gt;1.4.200&lt;/version&gt;
      &lt;scope&gt;test&lt;/scope&gt;
  &lt;/dependency&gt;
  </code></pre>