Refactor slides and assignments to focus less on @Profile in section on configuration in favour of more flexible approaches

[BjoernKW]

See https://reflectoring.io/dont-use-spring-profile-annotation/ and https://12factor.net/config

[BjoernKW]

Add slides on different ways of setting properties to configuration chapter:

• environment variables
• -D
• default values: ${VALUE:default}
• .env files
• property file precedence: https://docs.spring.io/spring-boot/docs/current/reference/html/features.html#features.external-config