How to make spring.data.mongodb.password have an optional value in Spring's application.propertties?

Question

I have a Spring Boot 3.3 application that accesses a MongoDB service. The application is deployed as a Container image to various stages. At some stages, using a username / password to connect to MongoDB is required, while other stages (like my local machine) don't. Changing the MongoDB setup is beyond my scope.

I am trying to address this using Spring's Common Application Properties for MongoDB autoconfiguration.

My application.properties look like this:

spring.data.mongodb.database=${MONGODB_DATABASE:documents}
spring.data.mongodb.host=${MONGODB_HOST:mongodb}
spring.data.mongodb.password=${MONGODB_PASSWORD:}
spring.data.mongodb.port=${MONGODB_PORT:27017}
spring.data.mongodb.username=${MONGODB_USERNAME:}

However, if for environments where MONGODB_PASSWORD the resulting property line is spring.data.mongodb.password= and the application refuses to start with:

Caused by: org.springframework.boot.context.properties.bind.BindException: Failed to bind properties under 'spring.data.mongodb.password' to char[]

I tried to make it run using a custom MongoDB client configuration and disabling auto-configuration:

@SpringBootApplication(exclude = {MongoAutoConfiguration.class, MongoDataAutoConfiguration.class})
public class MongoApplication {
    public static void main(String[] args) {
        SpringApplication.run(MongoApplication .class, args);
    }
}

and

@Configuration
public class MongoConfig extends AbstractMongoClientConfiguration {

    @Value("${spring.data.mongodb.password:}")
    private String password;

    [...]
    
    @Override
    protected String getDatabaseName() {
        return "documents";
    }

    @Bean
    @Override
    public MongoClient mongoClient() {
        
        if(this.password == null || this.password.isBlank()) {
           return MongoClients.create(
            String.formt("mongodb://%s:%d/%s", host, port, database)
           );
        } else {
           return MongoClients.create(
            String.formt("mongodb://%s:%s@%s:%d/%s", 
              username, password, host, port, database)
           );
        }
    }

    @Override
    protected boolean autoIndexCreation() {
        return true;
    }
}

This does work for application runtime but integration tests (using Testcontainers) fail, because auto-configuration is required to make @ServiceConnection annotation work.

Looking for hints ..