📝 Summary of Changes

Changes proposed in this pull request:

• ProviderVerifier Options initialiser accepts customHeader argument.
• customHeader is a dictionary of Strings.
• Only passes key-values that contain ASCII 32-127 characters only.
• When non-allowed characters are passed they are ignored and logged into console.
• Introduces a CharacterSet.headerASCIIAllowed containing only allowed characters.
• Unit tests Options initialisation with allowed and non-allowed characters for header
• Resolves Feature Request: Add Ability to Pass Custom Header for Verification #95

⚠️ Items of Note

Not verified with a provider.

💁 Example

let providerOptions = ProviderVerifier.Options(
	provider: .init(port: 8080),
	pactsSource: .directories(["/tmp/pacts"]),
	customHeader: ["Foo": "Bar 123abc_", "Bar": "BAZ"]
)

🔨 How To Test

1. Checkout the branch feature/provider_verification_headers_option.
2. Set up a provider project and prepare Options.
3. Include customHeader dictionary in Options.
4. Run provider verification tests.
5. Custom headers should be honoured.