The tag `spring.security.reached.filter.name` is only set if a
filter-name is available, otherwise the tag is omitted entirely. This
leads to issues with metric-exporters that don't support dynamic tags,
but rather expect tag-names of a metric to be always the same. The most
prominent example is the Prometheus-exporter.
Instead of omitting the tag if no filer-name is set, a none-value is
applied instead, making the tag-list consistent in all cases
Closes gh-13179
Dennis Frommknecht
af233a2a00