Allow referencing multiple secrets in additionalCertificates

[bianchi2]

There are cases when several self-signed certificates scattered across multiple K8S secrets need to be added to Java truststore. While there's a way to declare a custom additionalInitContainer, additionalVolumes and additionalVolumeMounts, this isn't trivial it requires knowledge of the DC Helm charts design.

This PR introduces an additional secretList value that makes it possible to reference multiple secrets with their respective keys in additionalCertificates stanza:

• existing secretName takes precedence if defined (existing behavior is unchanged i.e. it's a non-breaking change)
• secretList is a list of secret names and their respective keys
• each key will be used in subPath which makes it possible to mount certs from multiple secrets
• the resulting mounted file has <secret-name>-<key> format which makes it possible to have identical keys in different secrets

Checklist

• I have added unit tests
• I have applied the change to all applicable products
• The E2E test has passed (use e2e label)

[yzha645]

Suggested change

	secretList:
	secretList: []

Probably need to add [] if commented out the value, otherwise the list will be treated as a String.

[bianchi2]

oh, right. It was like that but removed when testing :) Fixed