[nifi] NiFi helm chart

[Hsankesara]

Description of the change

Since cetic helm-nifi is not being maintained any more, and we are planning to integrate the NiFI in the stack, it would be good to maintain NiFi helm charts. I have copied the helm chart from the cetic/helm-nifi repo. In future, I will work on updating the nifi version to NiFi 2.0.0.

Checklist

• Chart version bumped in Chart.yaml according to semver.
• Variables are documented in the README.md
• Title of the PR starts with chart name (e.g. [<name_of_the_chart>])

[yatharthranjan]

Hi, Thanks for this.

The CI is failing, you need to add a line for the new chart in the Makefile, similar to other charts with update-*. See previous PRs that added new external charts for reference.

Keeping a copy of the chart is a good idea, but I would not recommend using an archived (unmaintained) chart, as the updates and maintenance can be laborious. Instead, try finding alternative charts that are maintained, so when an update is made, you can just copy the update here, reducing the overheads. This is fine for now, but let's add an issue to update it in the future.
Some alternatives:

1. https://artifacthub.io/packages/helm/d4n/nifi
2. There is also a Kubernetes operator, but probably keep that for later - https://konpyutaika.github.io/nifikop/docs/1_concepts/1_start_here