AtoM Upgrade

backup Data and DB
get new AtoM-Version and save to /usr/share/nginx/atom[version number] [https://www.accesstomemory.org/de/docs/2.6/admin-manual/installation/linux/ubuntu-bionic/#option-1-download-the-tarball|link](download tarball)
create new DB named atom[version number]
grant access to the DB for the already existing mysql user atomuser
run Webinstaller. in case of 504 error, increase timeout. see https://groups.google.com/g/ica-atom-users/c/LKVkkvT1DkY/m/nVuzUQKJCwAJ
import old DB (only tables, not DB itself)
run upgrade task: php -d memory_limit=-1 symfony tools:upgrade-sql
regenerate digiteal object reference and thumbnail: php symfony digitalobject:regen-derivatives
restart services, clear cache
repopulate search