fix#604
- Assertions in `_helpers.tpl` were not effective, removed them
- Updated and indented assertions in `config.yaml`
- Added tests to check the assertions
Reviewed-on: https://gitea.com/gitea/helm-chart/pulls/611
Co-authored-by: pat-s <patrick.schratz@gmail.com>
Co-committed-by: pat-s <patrick.schratz@gmail.com>
