Add internet

[JimMadge]

✅ Checklist

• You have given your pull request a meaningful title (e.g. Enable foobar integration rather than 515 foobar).
• You are targeting the appropriate branch. If you're not certain which one this is, it should be develop.
• Your branch is up-to-date with the target branch (it probably was when you started, but it may have changed since then).

🚦 Depends on

⤴️ Summary

Adds the option to use 'internet' (case insensitive) in place of IP addresses in configuration.

🌂 Related issues

Closes #2229

🔬 Tests

Tested on a fresh deployment.
Writing the service tag works and I confirmed I can connect from a few different IP addresses

[github-actions]

Coverage report

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
data_safe_haven/config
config_sections.py
data_safe_haven/infrastructure/programs/sre
networking.py					71-76
data_safe_haven/types
enums.py
data_safe_haven/validators
validators.py
Project Total

This report was generated by python-coverage-comment-action

[JimMadge]

This won't work without some changes.

source_address_prefix can accept tags, but source_address_prefixes cannot.

[craddm]

LGTM