Improve String concatenation best practice

This change splits the "don't use String concatenation" best practice into two parts:

- A recommendation concerning performance: string concatenation is not efficient if the logger is off.
- A security recommendation: format string must be constants to prevent `{}` placeholder injection.

The `${dangerousLookup}` part of the example is removed, since lookups are not executed since version `2.15.0`
4 files changed