update kafka datasource documentation for new batch parameters (#781)

Author: Solvik

crowdsec-docs/docs/log_processor/data_sources/kafka.md

@@ -35,6 +35,30 @@ labels:
   type: nginx
 ```
 
+Adding a batch configuration:
+
+```yaml
+source: kafka
+brokers:
+  - "localhost:9093"
+topic: "my-topic"
+timeout: 5
+tls:
+  insecure_skip_verify: true
+  client_cert: /path/kafkaClient.certificate.pem
+  client_key: /path/kafkaClient.key
+  ca_cert: /path/ca.crt
+labels:
+  type: nginx
+batch:
+  min_bytes: 1024      # 1KB
+  max_bytes: 1048576   # 1MB
+  max_wait: 5s
+  queue_size: 1000
+  commit_interval: 1s
+```
+
+
 :::info
 The reader will always start from the latest offset.
 :::
@@ -60,7 +84,7 @@ Required.
 
 The consumer group id to use.
 
-Cannot be used with `partition`. 
+Cannot be used with `partition`.
 
 :::warning
 It is highly recommended to set this value, or crowdsec will only read logs from the 1st partition of the topic.
@@ -72,6 +96,12 @@ Read messages from the given partition. Mostly useful for debugging.
 
 Cannot be used with `group_id`.
 
+### `timeout`
+
+Maximum time to wait for new messages before returning an empty read.
+
+Default: 5
+
 ### `tls.insecure_skip_verify`
 
 To disable security checks on the certificate.
@@ -96,6 +126,35 @@ The CA certificate path.
 
 Optional, when you want to enable TLS with client certificate.
 
+### `batch.min_bytes`
+
+Minimum number of bytes to accumulate in the fetch buffer before returning results.
+
+Default: 1
+
+### `batch.max_bytes`
+
+Maximum number of bytes to fetch in one go.
+
+Default: 1048576 (1MB)
+
+### `batch.max_wait`
+
+Maximum time to wait before returning a fetch, even if `batch.min_bytes` isn’t reached.
+
+Default: 250ms
+
+### `batch.queue_size`
+
+Maximum number of messages to buffer internally before processing.
+
+Default: 100
+
+### `batch.commit_interval`
+
+Time interval between automatic commits of consumer offsets.
+
+Default: 0 (commit after every fetch)
 
 ### `source`
 
@@ -104,4 +163,3 @@ Must be `kafka`
 ## DSN and command-line
 
 This datasource does not support acquisition from the command line.
-