public String getConnectionString() {
        return String.format("mongodb://%s:%d", getHost(), getMappedPort(MongoDBContainerDef.MONGODB_INTERNAL_PORT));
    }
Gets a connection string url, unlike {@link #getReplicaSetUrl} this does not point to a
database
@return a connection url pointing to a mongodb instance
modules/mongodb/src/main/java/org/testcontainers/containers/MongoDBContainer.java