Release 0.18

[holgerfriedrich]

We should create a new release.

Since 0.17 in Jan, we had a few important things added

• Add check for Optional used as a field type #490
• Remove PMD rule SimplifyBooleanReturns #481
• tools were upgraded, for example PMD to support Java25
• Add PMD rules for default locale, charset and time zone #499
• Upgrade SpotBugs to 4.9.8 #501
• [checkstyle] OnlyTabIndentationCheck, OhInfXmlValidationCheck to report filename #506
• SAT 0.17 does not work with Java 25, as PMD fails on the new class files

Checkstyle cannot be upgraded, as long as we need Java 11 compatibility for the upgrade, see #494.
We will need to address this as well, but better not for 0.18.

Kai wants to release using this new mechanism:

• Introduce release process through GHA #497

[holgerfriedrich]

I would appreciate if we can finish the two pending PRs above, have some final comparisons of the output on core and add-ons, and then go for publishing a new release.