Bump mailgen from 2.0.30 to 2.0.32 in /backend

Bumps [mailgen](https://github.com/eladnava/mailgen) from 2.0.30 to 2.0.32.
- [Commits](https://github.com/eladnava/mailgen/commits)

---
updated-dependencies:
- dependency-name: mailgen
  dependency-version: 2.0.32
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]