Add possibility to decode base64 encoded parameters that are needed in clear text

[henninggross]

Issue

There are cases where one needs to have a multiline value (e.g. a certificate or a RSA key) in their template in clear text.

See this example (where TLS_CERTIFICATE and TLS_PRIVATE_KEY should be multiline values):

- apiVersion: route.openshift.io/v1
 kind: Route
...
 tls:
    certificate: ${TLS_CERTIFICATE}
    insecureEdgeTerminationPolicy: Redirect
    termination: edge
    key: ${TLS_PRIVATE_KEY}

When one now wants to add a key or a certificate to his .env.enc file he needs to base64 encode them and add a suffix to the parameter like this:
TLS_CERTIFICATE.B64=BASE_64_ENCODED_VALUE

This results in Tailor adding the base64 encoded value to the OpenShift template, which is not what one wants to happen with such parameters.

Possible Solution

A possible solution might be to introduce a suffix like .B64DECODE that tells Tailor to take the base64 encoded value and decode it before adding it to the template.