feat: more control on the migration job hook

[aballet]

I made the migration job hook configurable, so that it can be completely deleted.

Description

The rationale is that if someone deploys the chart with the --wait flag of helm, the deployment will wait forever (see #120).
We must remove the hook to solve this. The PR provides a way to do this without breaking changes.

References

Review Checklist

• I have clicked on "allow edits by maintainers".
• I have added documentation for new/changed functionality in this PR or in a PR to openfga.dev [Provide a link to any relevant PRs in the references section above]
• The correct base branch is being used, if not main
• I have added tests to validate that the change in functionality is working as expected