Use Helm genSelfSignedCert function

[bdalpe]

Preflight Checklist

• I could not find a solution in the existing issues, docs, nor discussions
• I have joined the ZITADEL chat

Describe your problem

Continuing discussion from #189 by @eliobischof's request.

Describe your ideal solution

This would replace the init container with the use of the Helm genSelfSignedCert function for simple certificate management.

#212 (and by extension #207) should also be considered for extended certificate management.

I propose the chart should work in three ways:

1. No certificate is generated. (this is the default: selfSignedCert.enabled=false)
2. Setting selfSignedCert.enabled=true uses the genSelfSignedCert function to create a new self-signed certificates instead of using the alpine/openssl container initJob.
3. Specifying a new existingSecret value in the Helm chart causes Zitadel to use externally-managed certificates. (i.e. created by cert-manager)

Version

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App version

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Additional Context

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