Deprecations

[andyundso]

This PR adds warnings to the code for a couple of things that will change in the next major release.

• Remove the web workflow.
  • It is still mentioned in the old documentation by Datatrans, but no longer in the new one. Instead, there they mention something called Secure Fields which appear to be the replacement for payment page?
• Mark the XML stuff as deprecated.
• Rename ::JSON::Authorize to ::JSON::Init
  • well, the API endpoint is actually named initialize, but that is a reserved keyword on Ruby. Still, Init should provide more clarity what the operation does than authorize. Closes Alias Datatrans::JSON::Transaction::Authorize to Datatrans::JSON::Transaction::Initialize #58.

[andyundso]

@visini think you asked to see the deprecation for Authorize.

[visini]

Great 🙏