Add event debug log for Refresh Grant to help debug Refresh Token Stuff

[robotdan]

Add event debug log for Refresh Grant to help debug Refresh Token Stuff

Description

It can be difficult to debug why the refresh grant fails. Add a debug event log to capture why we may return the following error:

{
  "error" : "invalid_grant",
  "error_description" : "The refresh_token is invalid.",
  "error_reason" : "refresh_token_not_found"
}

In some contexts it may also be helpful to keep track of the last n refresh token values when using one time use refresh tokens. I don't know how feasible this is - but it may be nice.

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