Release v1.9.0: notices "select" to "users", health check state lock fix, validation fixes, and more · canonical/pebble

What's Changed

chore(daemon): remove untrusted socket by @thp-canonical in #361
fix(daemon): Export error responders from daemon.response by @thp-canonical in #360
feat(wait): export cli.Wait function by @paul-rodriguez in #362
doc(state): say why we're not implementing warnings as notices yet by @benhoyt in #365
chore(daemon): port AccessChecker interface from snapd by @thp-canonical in #358
fix: validate whole plan, rather than topmost two layers by @tonyandrewmeyer in #363
feat(daemon): Add support for PEBBLE_COPY_ONCE. by @hpidcock in #352
fix(notices): replace "select=all" with "users=all" by @olivercalder in #368
fix(daemon): avoid acquiring state lock in health check endpoint by @benhoyt in #369
Update version to v1.9.0 for release; flesh out release instructions by @benhoyt in #370

Full Changelog: v1.8.0...v1.9.0