GitLab

# What does this PR do?

In title. Adds argument `--hostname` in router to support something like
`--hostname ::`. Tested with

```commandline
cargo run -- --port 8080 --hostname ::
curl -I -X GET 'http://[::1]:8080/health

'  # failed before this commit
```

Trigger CI

---------
Co-authored-by: Phil Chen <philchen2000@gmail.com>

Closes #478

Fixes #333

---------
Co-authored-by: Nicolas Patry <patry.nicolas@protonmail.com>

Co-authored-by: Nick Hill <nickhill@us.ibm.com>

close #125

closes #99

closes #65

Added validation logic