AtoM Upgrade

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backup Data and DB
get new AtoM-Version and save to /usr/share/nginx/atom[version number] 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 here
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