Add support for transformations in resource templates

[ryannedolan]

Summary

Templates frequently need the same variable in different forms, e.g. kafkaTopic and kafkaTopicLowerCase. Rather than require Resources to define multiple different formats of the same values, we now support simple transformations to be expressed in the templates themselves. This is similar to how Go/Helm templates allow transformation pipelines.

Details

The following forms are added:

• {{var toName}}, {{var:default toName}}: canonicalize the variable as a valid K8s object name.
• {{var toUpperCase}}, {{var:default toUpperCase}}: render in all upper case.
• {{var toLowerCase}}, {{var:default toLowerCase}}: render in all lower case.
• {{var concat}}, {{var:default concat}}: concatinate a multiline string into one line
• {{var concat toUpperCase}}: apply both transformations in sequence.

Testing

New unit test exercises these transformations.