Description

Currently, in order to turn random URL's off, you must have at least one random_url declaration with a type and enabled = false.

This PR makes the random_url config optional while deprecating the enabled field without breaking current configs.

Motivation and Context

Closes #121

How Has This Been Tested?

• cargo test
• fixtures
• manual

Changelog Entry

### Changed

- Make the `random_url` config optional

```toml
# enabled
random_url = { type = "petname", words = 2, separator = "-" }

# disabled 
# random_url = { type = "petname", words = 2, separator = "-" }
```

### Deprecated

- Deprecate `enabled` field in `random_url`

Types of Changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (no code change)
• Refactor (refactoring production code)
• Other

Checklist:

• My code follows the code style of this project.
• I have updated the documentation accordingly.
• I have formatted the code with rustfmt.
• I checked the lints with clippy.
• I have added tests to cover my changes.
• All new and existing tests passed.