Use pydantic for transformation validation (#1606)

# Description

Start using the newly created `TransformationYAML` for validation in the
`cdf build` command.

## Changelog

- [x] Patch
- [ ] Minor
- [ ] Skip

## cdf

### Improved

- In the `cdf build` command improved feedback if transformations
configurations is not following the specifications.

## templates

No changes.
