Add custom metadata to AWS logs (using firelens for logging and Kinesis Firehose, AWS CDK)

Question

Current setup is this :

ECS Task with 2 containers,

1. App Container
2. Logging Container (fluentbit, created by default after using the firelens logging)

The logs generated from the App container are sent to a Kinesis Firehose Stream , and then this stream sends them to an S3 bucket.

My question is how can i add some additional metadata to the logs (key:value) so that way i can filter them at the OpenSearch(which is the final destination)

This is the code in CDK for the logging part

logging=ecs.LogDrivers.firelens(options={
                    "Name": "firehose",
                    "region": "us-east-1",
                    "delivery_stream":"kinesis-stream"
                    }
                )

i have tried adding, env=["string"],
labels=["string"],
tag="string"

but they are not added to the logs