Evaluate trust namespace value as template

[heruan]

When installing trust-manager as a subchart (i.e. dependency) it would be useful to automatically set the trust namespace value to the release namespace, or another dynamic value. At the moment this is unfortunately not possibile since the app.trust.namespace value is evaluated as-is and so it needs to be always explicitly specified if you don't want the default one.

This can be easily solved if the value were evaluated as a template, e.g.

 metadata:
   name: {{ include "trust-manager.name" . }}
-  namespace: {{ .Values.app.trust.namespace }}
+  namespace: {{ tpl .Values.app.trust.namespace . }}

Then it would be possibile to set the trust namespace dynamically, e.g.

# Subchart configuration when trust-manager is a dependency
trust-manager:
  app:
    trust:
      namespace: {{ .Release.Namespace }}

Is this something that might be worth a PR? I'd be happy to contribute!