[Helm] chart can't be install without defining .Values.rsa or .Values.rsa.existingSecret

[michMartineau]

Describe the bug
commit 6ee8d1f introduced .Values.rsa.existingSecret.
It is not possible anymore to install the chart without defining rsa.

As .Values.rsa is nil by default, and it is a parent of existingSecret, the following change (runner.yaml) fails.

secretName: {{ default "robusta-auth-config-secret" .Values.rsa.existingSecret }}

To Reproduce
Steps to reproduce the behavior:

• install the chart without defining .Values.rsa or .Values.rsa.existingSecret

Expected behavior
The chart should be installed without .Values.rsa or .Values.rsa.existingSecret defined

Additional context
Proposal: #1161

[pavangudiwada]

Closing since its merged #1161