added fluentd-record-modifier plugin

[alexxed]

because it's faster than record-transformer

Q	A
Bug fix?	no
New feature?	yes
API breaks?	no
Deprecations?	no
Related tickets	fixes #348
License	Apache 2.0

What's in this PR?

Added the fluentd record-modifier plugin.

Why?

It's at least twice as fast compared to record-transformer

Checklist

• Error handling code meets the guideline
• Logging code meets the guideline (TODO)
• User guide and development docs updated (if needed)
• Related Helm chart(s) updated (if needed)

[alexxed]

Needs a manual test.

[tarokkk]

LGTM ;) needs some testing thought

[ahma]

Great Job Thanks @alexxed LGTM

[alexxed]

Tested with this logging configuration and a cluster flow that sends to sumo logic:

apiVersion: logging.banzaicloud.io/v1beta1
kind: Logging
metadata:
  name: logging
  namespace: logging
spec:
  enableRecreateWorkloadOnImmutableFieldChange: true
  fluentd:
    image:
        repository: alexandruszaszacquia/fluentd
        tag: record-modifier
        pullPolicy: IfNotPresent
    metrics:
      port: 24231
  fluentbit:
    metrics:
      port: 2020
  controlNamespace: logging

cluster flow

apiVersion: logging.banzaicloud.io/v1beta1
kind: ClusterFlow
metadata:
  name: clusterflow-forward-logs-to-sumologic
  namespace: logging
spec:
  filters:
    - record_modifier:
       records:
       - stage: dev
       - aws_local_ip: ${record.dig("kubernetes", "host").to_s.gsub(/ip-([^\.]+)\.ec2\.internal/, '\1').gsub(/-/, '.')}
  selectors: {}
  outputRefs:
    - output-acquia-sumologic

and got this record:

I haven't manually tested the other options, e.g. replace, whitelist; but there's a unit test with all of them. As long as that is cross referenced with the plugin's documentation, that should be good to go.