[DOC] how to build nested telegraf.conf

The instructions are a bit vague and I'm unable to sort how to build a telegraf.conf like:

```toml
[[inputs.kafka_consumer]]
brokers = [
"kafka-bootstrap.kafka:9092"
]
client_id = "opmon-telegraf"
consumer_group = "opmon-telegraf"
data_format = "json_v2"
topics = [
"opmon"
]
version = "3.4.0"
[[inputs.kafka_consumer.json_v2]]
measurement_name_path = "measurement"
timestamp_format = "2023-07-13T14:59:51Z"
timestamp_path = "time"
[[inputs.kafka_consumer.json_v2.object]]
tags = [ "tags" ]
[inputs.kafka_consumer.json_v2.object.fields]
key = "fields"
```

Locate the Helm chart documentation that explains building telegraf.conf and compare its instructions with the nested TOML example in this issue. Clarify the steps needed to reproduce the shown inputs.kafka_consumer configuration, then verify that the documentation accurately reflects the example.

Written by the indexing model from the issue text.