Xero cloud accounting API access app for Scheduling on Windows PC

Hi - I urgently need a script/app that will connect to our Xero cloud accounts data and download data from the various tables to a PC. The download process needs to be scriptable and run on a schedule . The local data should be saved as a JSON file per Xero table - I already have PS code to that I can modify to convert this in to a CSV file which is what is currently used in our reporting. It looks like all the required access and API details are documented by Xero, but this is beyond my PS skillset. [login to view URL] [login to view URL] Ideally looking for this to be written as a Powershell script, but this particular project could be a VB.NET command line app as the .NET approach seems to be covered by documentation/examples. It's "possible" that we could accommodate an approach based on PHP as that is a platform that we are increasingly looking to deploy in our production environment. As I understand, the process needs to use OAUTH2 to authenticate, and then the API calls are fairly straightforward. The minimum I need is something that will complete the OAUTH authentication and download one table to JSON file - I can then copy/develop the code to add other tables as required. I have other projects that need to be completed, and would really like to build a partnership with one or more experienced developers/coders who are knowledgeable, proactive and reliable and can turn their hand to a variety of projects, potentially using Pwershell, VB.NET and PHP/MySQL... Obviously this project will expose the developer to sensitive business information, so we're also looking for someone with a good reputation/working history on Upwork!