out_kafka: Add dynamic/static headers support

[DIFRIN]

Currently,the output kafka plugin not support headers. The goal of this pull-request is to add support for dynamic/static headers to the output kafka plugin

No issue

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Testing
Before we can approve your change; please submit the following in a comment:

• docker run --rm --network kafka_default -e value_test='${text}' -it fluent/fluent-bit-local:latest -i dummy -p dummy='{"text": "hello world"}' -p samples=1 -o kafka -p brokers=kafka:9092 -p topics=test_fluentbit -p header="key2 <text>" -vvv
  -###################################################
  Fluent Bit v3.0.0

• Copyright (C) 2015-2024 The Fluent Bit Authors
• Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
• https://fluentbit.io

. __ . __ ________
_ ____/| | __ __ ____ / | _ _|/ | ___ _
| __) | | | | _/ __ \ / \ __\ | | / \ _\ \ / / ( <
| \ | || | /\ /| | \ | | | \ || | \ / /
_ / |/____/ _ >| /| |____ /||| _/ /______ /
/ / / / /

[2024/03/15 12:25:59] [ info] Configuration:
[2024/03/15 12:25:59] [ info] flush time | 1.000000 seconds
[2024/03/15 12:25:59] [ info] grace | 5 seconds
[2024/03/15 12:25:59] [ info] daemon | 0
[2024/03/15 12:25:59] [ info] ___________
[2024/03/15 12:25:59] [ info] inputs:
[2024/03/15 12:25:59] [ info] dummy
[2024/03/15 12:25:59] [ info] ___________
[2024/03/15 12:25:59] [ info] filters:
[2024/03/15 12:25:59] [ info] ___________
[2024/03/15 12:25:59] [ info] outputs:
[2024/03/15 12:25:59] [ info] kafka.0
[2024/03/15 12:25:59] [ info] ___________
[2024/03/15 12:25:59] [ info] collectors:
[2024/03/15 12:25:59] [ info] [fluent bit] version=3.0.0, commit=9d9ac68a2b, pid=1
[2024/03/15 12:25:59] [debug] [engine] coroutine stack size: 24576 bytes (24.0K)
[2024/03/15 12:25:59] [ info] [storage] ver=1.5.1, type=memory, sync=normal, checksum=off, max_chunks_up=128
[2024/03/15 12:25:59] [ info] [cmetrics] version=0.7.0
[2024/03/15 12:25:59] [ info] [ctraces ] version=0.4.0
[2024/03/15 12:25:59] [ info] [input:dummy:dummy.0] initializing
[2024/03/15 12:25:59] [ info] [input:dummy:dummy.0] storage_strategy='memory' (memory only)
[2024/03/15 12:25:59] [debug] [dummy:dummy.0] created event channels: read=21 write=22
[2024/03/15 12:25:59] [debug] [kafka:kafka.0] created event channels: read=23 write=24
[2024/03/15 12:25:59] [ info] [output:kafka:kafka.0] Starting kafka output init
[2024/03/15 12:25:59] [ info] [output:kafka:kafka.0] brokers='kafka:9092' topics='test_fluentbit'
[2024/03/15 12:25:59] [ info] [sp] stream processor started
[2024/03/15 12:26:00] [debug] [input chunk] update output instances with new chunk size diff=39, records=1, input=dummy.0
{"text"=>"hello world"}[2024/03/15 12:26:01] [debug] [task] created task=0x7f423f8366e0 id=0 OK
[2024/03/15 12:26:01] [debug] in produce_message

[2024/03/15 12:26:01] [debug] setting message headers
[2024/03/15 12:26:01] [debug] found header key2 with value
[2024/03/15 12:26:01] [debug] header key2 is part of the msg, field name :
[2024/03/15 12:26:01] [debug] key matches a field in the message
[2024/03/15 12:26:01] [ info] [output:kafka:kafka.0] Sending message completed
[2024/03/15 12:26:01] [debug] [output:kafka:kafka.0] enqueued message (53 bytes) for topic 'test_fluentbit'
[2024/03/15 12:26:01] [debug] [out flush] cb_destroy coro_id=0
[2024/03/15 12:26:01] [debug] [task] destroy task=0x7f423f8366e0 (task_id=0)

############################################################

• Resulting records in kafka:
  kafka-console-consumer --topic test_fluentbit --bootstrap-server kafka:9092 --property print.headers=true
  key2:hello world {"@timestamp":1710505560.027627,"text":"hello world"}

• [N/A ] Attached Valgrind output that shows no leaks or memory corruption was found

Documentation
[https://github.com/fluent/fluent-bit-docs/pull/1341]

Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

[patrick-stephens]

Can you sort the DCO failure? This cannot be merged without it

[DIFRIN]

@patrick-stephens DCO added to the commits

[DIFRIN]

@patrick-stephens @edsiper this is the message of the failed check

The following tests FAILED: 46 - flb-rt-out_http (Failed) Error: Process completed with exit code 8.

it's not linked to the PR content

[patrick-stephens]

Possibly the test failure is related to #9023