deprecate three methods for version 2.0

[hyuraku]

Description

apply Faraday#deprecate to three deprecated methods for version 2.0.

• Request#method
• Connection#token_auth
• Connection#authorization

related with #1438

Todos

List any remaining work that needs to be done, i.e:

• Tests
• Documentation

Additional Notes

Optional section

[iMacTia]

Thank you @hyuraku, one thing I'm not entirely happy about is that the existing warnings not only communicate which method has been deprecated and from where it was called, but they also provide a hint as to how to address them, and a link to the relevant documentation.
Simply replacing them with Faraday::Deprecate will make that information disappear 😢

Do you think it would be possible to extend #deprecate so that it accepts an additional (optional) parameter that we can use to provide a "custom message" on some deprecation warnings, and use that new parameter in these cases?

[hyuraku]

@iMacTia

Do you think it would be possible to extend #deprecate so that it accepts an additional (optional) parameter that we can use to provide a "custom message" on some deprecation warnings, and use that new parameter in these cases?

I guess it's better to add custom_message as the args to Faraday::Deprecate#deprecate, How about?

• Before change

    def deprecate(name, repl, ver)
         --< omitted >--
          msg = [
            "NOTE: #{target_message} is deprecated",
            repl == :none ? ' with no replacement' : "; use #{repl} instead. ",
            "It will be removed in or after version #{gem_ver}",
            "\n#{target}#{name} called from #{Gem.location_of_caller.join(':')}"
          ]

• After change

def deprecate(name, repl, ver, custom_message)
       --< omitted >--
      msg = [
            "NOTE: #{target_message} is deprecated",
            repl == :none ? ' with no replacement' : "; use #{repl} instead. ",
            "It will be removed in or after version #{gem_ver}",
            custom_message
            "\n#{target}#{name} called from #{Gem.location_of_caller.join(':')}"
          ]
          
end

[iMacTia]

Yeah, that would be perfect to share the link to the documentation or any other free-text valuable context on the deprecation 🙏!

[hyuraku]

@iMacTia
Could you review this PR again?

[iMacTia]

Thank you @hyuraku for the changes and @olleolleolle for spotting the leftover line. LGTM!