Provide the ability to combine multiple references when setting a single helm value

[jcooklin]

What problem are you facing?

Using the aws provider and creating a redis server I am unable to install the chart goharbor (https://helm.goharbor.io) using the helm provider since I am unable to provide a value for "redis.external.addr" which requires the form :. The connection details which are written by the aws provider give the host and port as separate keys however since this chart combines them I unable to easily use the helm provider. The helm provider provides a direct replacement value substitution but no transformation or templating.

How could Crossplane help solve your problem?

Some kind of basic templating would be really helpful. Given an array of references (config or secrets) and a template "%s:%s this issue could be easily addressed.