Whenever possible, please amend the doc/release-notes.md within the pull that introduces a new fancy feature or breaks compatibility.

If this is not possible, mention the pull here, so it can be taken care of later.

FYI 0.17.0 release notes are up at the wiki: https://github.com/bitcoin-core/bitcoin-devwiki/wiki/0.17.0-Release-notes

(you don't need to mention all changes here, only those that have specific changes that the user needs to be aware of)