This function signs an ApiRequest or an HttpRequest.
signer should be constructed using Oauth1Helper.createSigner.
req should be a code_data_generic_ApiRequest or a code_model_flows_processors_http_HttpRequest.
key and secret are both strings and are mandatory.
token, tokenSecret, verifier, callback, and authHeader are all Option[String] and are not mandatory. AuthHeader will default to "Authorization" if not specified.
Body
function(signer,req,key,secret,token,tokenSecret,verifier,callback,authHeader){...}