As found by
OPENIDM-12696, Linkedin no longer works as part of our generic OAuth2Client implementation.
Upon investigation, it has been discovered this failure is due to our addition of PKCE suppport. Linkedin fails on the accessToken endpoint when any additional parameters with an "Access Denied". Linkedin doesnt support PKCE unless it is for a native application https://docs.microsoft.com/en-us/linkedin/shared/authentication/authorization-code-flow-native?context=linkedin/sales/context
Additionally, as of May 1 2019, Linkedin no longer supports its v1 APIs. Their v2 API now separates the retrieval of profile information and email address into two separate APIs. Due to this we now need a custom linkedin client to accommodate their new APIs.
A new linkedin client to support the v2 API