As explained in my email the OAUTH is pretty straight forward. Lightspeed provides:
API Key: 1234b76ac30fee47a0510c0430d465524
API secret: 12345n4a4a7dc5e676fe056630f2afa3
These are fake keys BTW.
In order to GET a list of products you can use URL below
The same goes for a POST. In the microflow you can add the JSON you want to post. Litghspeed documentation explains the format of the JSON string.
There are more OAuth modules in the appstore and none are from Mendix itself so I do not know which module you looked at.
You have the Social authentication from Andries Smit (https://appstore.home.mendix.com/link/app/1206/Flock-of-Birds/Social-Authentication ) and you have the Open Authentication module from Erwin 't Hoen (https://appstore.home.mendix.com/link/app/1414/FlowFabric-BV/Open-Authentication-Module ). The Open Authentication module has some good documentation on how to start. Erwin is very active on the forum so if you run into problems he probably is willing to give you pointers.
And it seems that in this forum post is about the same use case https://forum.mendix.com/link/questions/85655
I've done a several oAuth implementations (with Google and ADFS). I think a can create a generic module but don't expect this be ready for the appstore the upcoming days ;) when do you need it?