[FEATURE] add subject and body to email viewhelper

[kaystrobach]

Upgrade instructions

Review instructions

Checklist

• [ ] Code follows the PSR-2 coding style
• [ ] Tests have been created, run and adjusted as needed
• [ ] The PR is created against the lowest maintained branch
• [ ] Reviewer - PR Title is brief but complete and starts with FEATURE|TASK|BUGFIX
• [ ] Reviewer - The first section explains the change briefly for change-logs
• [ ] Reviewer - Breaking Changes are marked with !!! and have upgrade-instructions

[kaystrobach]

maybe also backport that to 8.x - thank you