== real process, real environment: binding demo.relaxed.api-key ==

canonical property : demo.relaxed.api-key
(MISS) means the property was not found and the declared default was used

--- as an operating-system environment variable ---

$ DEMO_RELAXED_API_KEY=secret-value java -jar target/configuration-properties-1.0.0.jar
env-var-set        : DEMO_RELAXED_API_KEY=secret-value
@ConfigurationProps: secret-value
@Value             : secret-value
Environment.get    : secret-value

$ DEMO_RELAXED_APIKEY=secret-value java -jar target/configuration-properties-1.0.0.jar
env-var-set        : DEMO_RELAXED_APIKEY=secret-value
@ConfigurationProps: secret-value
@Value             : secret-value
Environment.get    : secret-value

--- as a JVM system property (-D), i.e. the 'map' rows of the matrix ---

$ java -Ddemo.relaxed.api-key=secret-value -jar target/configuration-properties-1.0.0.jar
@ConfigurationProps: secret-value
@Value             : secret-value
Environment.get    : secret-value

$ java -Ddemo.relaxed.apiKey=secret-value -jar target/configuration-properties-1.0.0.jar
@ConfigurationProps: secret-value
@Value             : secret-value
Environment.get    : secret-value

$ java -Ddemo.relaxed.apikey=secret-value -jar target/configuration-properties-1.0.0.jar
@ConfigurationProps: secret-value
@Value             : secret-value
Environment.get    : secret-value

$ java -Ddemo.relaxed.api.key=secret-value -jar target/configuration-properties-1.0.0.jar
@ConfigurationProps: (unset)
@Value             : (MISS)
Environment.get    : (MISS)

The last one is not a spelling of the property. api.key is two name elements;
api-key is one. Nothing relaxed will ever join them.