MongoDB with Hibernate OGM and Spring-Boot - persistence.xml Authentication doesn't go against specified Database

Question

I'm currently working on a simple demo application to show example CRUD with MongoDB Hibernate OGM and Spring-Boot. I have a local MongoDB with 2 users.

 use admin
    db.createUser(
      {
        user: "useradmin",
        pwd: "password,
        roles: [ { role: "userAdminAnyDatabase", db: "admin" } ]
      }
    )

use TestDB
db.createUser(
  {
    user: "test",
    pwd: "test123",
    roles: [ { role: "readWrite", db: "TestDB" } ]
  }
)

My persistence.xml file looks like this:

    <?xml version="1.0" encoding="utf-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
    version="2.0">
    <persistence-unit name="ogm-mongodb"
        transaction-type="JTA">
        <provider>org.hibernate.ogm.jpa.HibernateOgmPersistence</provider>
        <properties>
            <property name="hibernate.ogm.datastore.provider" value="MONGODB" />
            <property name="hibernate.ogm.datastore.database" value="TestDB" />
            <property name="hibernate.ogm.datastore.create_database" value="true" />
            <property name="hibernate.ogm.datastore.host" value="127.0.0.1" />
            <property name="hibernate.ogm.datastore.port" value="27017" />
            <property name="hibernate.ogm.datastore.username" value="useradmin"/>
            <property name="hibernate.ogm.datastore.password" value="password"/>
        </properties>
    </persistence-unit>
</persistence>

If I start my spring-Boot application and trigger the endpoint to write test data to the MongoDB i get an exception because the useradmin doesn't have read or write access to the TestDB. So far so good.
But if I change the username and password property in the persistence.xml to test and test123 I get an exception on startup of the spring app:

Unable to start datastore provider

Cause:

Unable to connect to MongoDB instance: Exception authenticating MongoCredential{mechanism=SCRAM-SHA-1, userName='test', source='admin', password=<hidden>, mechanismProperties={}}

I suspect the application tries to authenticate against admin and not the TestDB

My pom.xml dependencies are here:

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <version>2.5.4</version>
        </dependency>

        <dependency>
            <groupId>org.hibernate.ogm</groupId>
            <artifactId>hibernate-ogm-mongodb</artifactId>
            <version>5.4.0.Final</version>
        </dependency>
        <dependency>
            <groupId>org.mongodb</groupId>
            <artifactId>mongodb-driver</artifactId>
            <version>3.12.10</version>
        </dependency>
        <dependency>
            <groupId>org.jboss.narayana.jta</groupId>
            <artifactId>narayana-jta</artifactId>
            <version>5.12.1.Final</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <version>2.5.4</version>
            <scope>test</scope>
        </dependency>

The Error originates in my ExampleService class according to the stacktrace

@Service
public class ExampleService {

    EntityManagerFactory emf;
    EntityManager em;
    TransactionManager tm;

    public ExampleService() {
        emf = Persistence.createEntityManagerFactory("ogm-mongodb"); //Error here
        em = emf.createEntityManager();
        tm = com.arjuna.ats.jta.TransactionManager.transactionManager();
    }
...

Do I have an Error in my configuration or persistence.xml? Thanks for any help in advance