NIFI-9367 Update README.md

[laurentedel]

how to find generated credentials in the logs
adding default passwords security policy

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Enables X functionality; fixes bug NIFI-YYYY.

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[exceptionfactory]

Thanks for the pull request @laurentedel! As noted in the Pull Request checklist, each change requires an associated Jira issue number, so please open an issue in the Apache NiFi Jira board. You can also join the Developers mailing list and request Jira contributor access so that you can assign the issue to yourself. After opening the Jira issue, you can update this pull request to include the Jira number.

[laurentedel]

This commit aims to resolve NIFI-9367 for Docker image usage details and clarification

[exceptionfactory]

Thanks for creating a Jira issue and updating the pull request @laurentedel. Adding details to the Docker README is a helpful improvement, thanks for the contribution! I made several suggestions to align the wording with the project README.md, and also to correct spelling in a couple places.

[laurentedel]

Thank you for all your very valuable suggestions @exceptionfactory !

[exceptionfactory]

Thanks for making the changes @laurentedel, the latest updates look good! +1 Merging.