Swift property wrapper for basic KeychainAccess usage.

This micro-framework provides a very limited and opiniated use of the KeychainAccess framework (see Package.swift dependencies):

• It provides access to a specified keychain key via a property wrapper for any Codable value - which allows to easily safe bigger structures into the Keychain
• It allows to switch on biometric access to that property, which will require authentication when the property is read
• It will cache the last retrieved value during runtime of the app, to not trigger any biometric authentication when this property needs to be read a second time during runtime

    // Simple value
    @KeychainProperty(valueKey: "1FATokenData") 
    private var tokens1FA: TokenData?
    
    /// Biometric authentication for a value
    @KeychainProperty(
        valueKey: "2FATokenData", 
        requiresBiometry: true
    )
    private var tokens2FA: TokenData?

As mentioned, this thing does only one particular thing, and it might be a good idea to extend upon it:

• Introduce a timeout at which the cache will reset
• Migration support
• ...

Thanks to the Framework KeychainAccess this micro-framework is based on.

MIT