Add conditional install for CA and Prod ClusterIssuer

[iyannsch]

Currently, the theia.cloud-base helmchart always installs three ClusterIssuer: issuerca, issuerprod, and issuerstaging. This might make sense for a testing environment or a cluster just serving Theia but might be unnecessary for those environments in which ClusterIssuers are already handled.
According to @jfaltermeier it would be useful to opt-out of automatic installs of issuerca, issuerprod. Fixes #50.

My changes introduce two new useExisting values that disable the creation of new ClusterIssuer. issuerstaging is always created as required for testing.

[lucas-koehler]

Hi @iyannsch , thank you very much for the PR :)

Instead of using flag useExisting, I'd prefer using enable: We use this already in other parts of the helm charts to toggle installation and AFAIK it is quite common to use this in Helm charts.

With this, you can also simplify the if checks in the cluster issuers, e.g. to if .Values.issuerca.enable.

Please also increase the version counter after the next. in the version property in charts/theia.cloud-base/Chart.yaml.

Note that I'll be on vacation from 26.6 to 2.7. in case you push a change in the meantime. I can re-review afterwards :)

[iyannsch]

Thanks for you comment and feedback @lucas-koehler,

I addressed your changes and request a new review from your end :)

Please do enjoy your vacation, looking forward to hearing from you in July ☺️

[lucas-koehler]

Hi @iyannsch , thanks for the updates! I added some suggestions that simplify the if checks and enable the issuers by default. The latter resembles the previous behavior.

Apparently, conflicting changes have been merged in the meantime. Please rebase the changes :)

[iyannsch]

@lucas-koehler Thanks for your review!
I incorporated all your suggestions and rebased to ensure a clean merge :)

[lucas-koehler]

Looks good to me now! Thanks for the updates and the rebase @iyannsch :)