How to configure Basic Auth with Symfony

Hi,

I couldn't find it in the documentation, but what would be the prefered way to configure basic auth for the elastic search endpoint when using the Symfony configuration?

Currently I'm using the provided example mainly:
```yaml
elastically:
connections:
# You can create multiple clients
default:
# Any Elastica option works here
client:
hosts:
- 'es.example.com'

# Path to the mapping directory (in YAML)
mapping_directory: '%kernel.project_dir%/config/elasticsearch'

# Size of the bulk sent to Elasticsearch (default to 100)
bulk_size: 100

# If you want to add a prefix for your index in elasticsearch (you can still call it by its base name everywhere!)
prefix: '%kernel.environment%'

# Use HttpClient component
transport_config:
http_client: 'Psr\Http\Client\ClientInterface'
```

But I'm unsure as to where to configure the username and password