chore: implement user link claims as a typed golang object (#15502)

Move claims from a `debug` column to an actual typed column to be used.
This does not functionally change anything, it just adds some Go typing to build
on.

coderd/httpmw/apikey.go

@@ -377,7 +377,7 @@ func ExtractAPIKey(rw http.ResponseWriter, r *http.Request, cfg ExtractAPIKeyCon
 				OAuthExpiry:            link.OAuthExpiry,
 				// Refresh should keep the same debug context because we use
 				// the original claims for the group/role sync.
-				DebugContext: link.DebugContext,
+				Claims: link.Claims,
 			})
 			if err != nil {
 				return write(http.StatusInternalServerError, codersdk.Response{