Allow @DataNeo4jTest to autoconfigure an embedded test instance

https://github.com/spring-projects/spring-data-neo4j/issues/2316#issuecomment-873918857

reading https://docs.spring.io/spring-data/neo4j/docs/current/reference/html/#dataneo4jtest

and wondering, couldn't this be easier? I mean how often am I going to care about the actual username and password, couldn't I just inject, for example, a Neo4j and have it configured by default when I use @DataNeo4jTest depending on what's on the classpath. I don't really see why the sample test should need to do anything other than this (well, it doesn't seem as this is setting up any data, but other than that...)

@DataNeo4jTest
class MovieRepositoryTest {

        @Test
        public void findSomethingShouldWork(@Autowired Neo4jClient client) {

                Optional<Long> result = client.query("MATCH (n) RETURN COUNT(n)")
                        .fetchAs(Long.class)
                        .one();
                assertThat(result).hasValue(0L);
        }
}

to contrast the examples in neo4j to reinforce my ask

@DataJpaTest
class MyRepositoryTests {

    @Autowired
    private TestEntityManager entityManager;

    @Autowired
    private UserRepository repository;

    @Test
    void testExample() throws Exception {
        this.entityManager.persist(new User("sboot", "1234"));
        User user = this.repository.findByUsername("sboot");
        assertThat(user.getUsername()).isEqualTo("sboot");
        assertThat(user.getEmployeeNumber()).isEqualTo("1234");
    }

}

the data jpa test doesn't require you to spend time in each test configuring the entity manager.

Start by reading the linked @DataNeo4jTest reference documentation and the referenced Spring Data Neo4j issue comment. Define done as a @DataNeo4jTest test being able to autowire Neo4jClient with an embedded test instance selected from the classpath, without per-test username or password configuration.