Send email on first login

• Related issue: https://gitlab.e.foundation/e/backlog/-/issues/4888
• Email Template: https://mc.sendgrid.com/dynamic-templates/d-fd8cdc9225f54e688b1513656620ddcb/version/cdb1d6a1-7b5b-47a7-9f84-191eed813e3b/editor

System config:

docker exec -u www-data dev01_nextcloud /var/www/html/occ config:system:set sendgrid_api_key --value='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'

docker exec -u www-data dev01_nextcloud /var/www/html/occ config:system:set welcome_sendgrid_template_ids en --value='d-fd8cdc9225f54e688b1513656620ddcb'
docker exec -u www-data dev01_nextcloud /var/www/html/occ config:system:set welcome_sendgrid_template_ids de --value='d-63917b5f69c84367aee679d56ba48c85'
docker exec -u www-data dev01_nextcloud /var/www/html/occ config:system:set welcome_sendgrid_template_ids es --value='d-6d1e82071b4541799f10d2bb5b9ae41d'
docker exec -u www-data dev01_nextcloud /var/www/html/occ config:system:set welcome_sendgrid_template_ids it --value='d-eac0d050c35342f3960e02e0582ee989'
docker exec -u www-data dev01_nextcloud /var/www/html/occ config:system:set welcome_sendgrid_template_ids fr --value='d-9daf8a4bd59144189033ecb63e25e679'