Expressions

canary-checker can be extended using expressions in 3 ways:

1. Display Formatting provides the ability to customize the info or error message for a health check.
2. Health Evaluation provides the ability to define whether a check is considered passing or failing based on the result
3. Transforms allow arbitrary transformations to:
   • Split a check into multiple (e.g. If they are all received in a single JSON)
   • Modify check results (e.g. Add labels, change severity etc)
   • Change the namespace target of a check
   • Save part of the result (e.g. last log age) to be used in future checks