fix(authentik): add option to set serviceaccount

[wrenix]

I like to follow security guide lines, which say nobody should use the "default" serviceAccount of an namespace ...

so i like to create my own serviceAccount and assign it with this helm-chart.

PS: maybe it is also needed for #146

[wrenix]

That is not BSI conform to use default serviceAccount, take a look in: APP.4.4.A9 Nutzung von Kubernetes Service-Accounts

https://www.bsi.bund.de/SharedDocs/Downloads/DE/BSI/Grundschutz/IT-GS-Kompendium_Einzel_PDFs_2022/06_APP_Anwendungen/APP_4_4_Kubernetes_Edition_2022.pdf?__blob=publicationFile&v=3

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if you prefer to stop using the mount of the serviceaccount, it will break additional feature which user of this helm-chart could needed (e.g. #146).

[wrenix]

we miss the version bump -> does anybody create one, or should i create a PullRequest for it.

[rissson]

We bump the chart when we release authentik