Potential expression conflicts

[rsenden]

Configuration files may contain ${...} placeholders to reference environment variables/system properties. However, some configuration properties (*Expression) may define expressions that also contain ${...} placeholders. These template placeholders should not be evaluated when the configuration file is loaded, but rather should be passed as-is to the relevant code,

Spring seems to pass ${...} placeholders as-is if the placeholder cannot be resolved as an environment variable or system property, which fits our use cases.

However, potentially this could result in conflicts, for example if an environment variable is defined with the same name as used in a template expression.

It would be much better if we would use different syntax for placeholders resolved at configuration time, and placeholders resolved at some later time.