Add support for additional params in auth url

[mpgxvii]

• Add support for additional params in the AuthorizationPage to allow redirecting directly to Fitbit auth and allow redirecting to a custom URL after authorization is complete (using redirect=true and redirect_uri=URL-HERE
• Also added improvements to the AuthorzationCompletePage
• Needed by the SEP portal (since user will self authorise and need to be redirected back to the SEP portal)

[yatharthranjan]

Just reported by callum, if there is an error when linking fitbit (eg - user has already connected fitbit ), then the error is still showin in rest-sources-auth UI. Ideally, it should redirect directly back to the SEP UI if redirect=true is set in the params, and should include the error in the url params.