class for Billwerk.com REST connections; returns BillwerkRestClient::BillwerkRestClient objects 
supports the following options:
"client_id" (optional): the billwerk.com client_id 
"client_secret" (mandatory): the billwerk.com client_secret 
"connect_timeout": connection timeout to use in milliseconds 
"content_encoding": this sets the send encoding (if the "send_encoding" option is not set) and the requested response encoding; for possible values, see EncodingSupport 
"data": see RestClient::RestClient::DataSerializationOptions for possible values when used with the null REST schema validator; the default is "auto"  
"error_passthru": if True then HTTP status codes indicating errors will not cause an HTTP-CLIENT-RECEIVE-ERROR exception to be raised, rather such responses will be passed through to the caller like any other response 
"http_version": HTTP version to use ("1.0" or "1.1", defaults to "1.1") 
"max_redirects": maximum redirects to support 
"proxy": proxy URL to use 
"send_encoding": a send data encoding option or the value "auto" which means to use automatic encoding; if not present defaults to no content-encoding on sent message bodies 
"swagger": the path to a Swagger 2.0 REST schema file for runtime API validation (see the Swagger module) 
"timeout": transfer timeout to use in milliseconds 
- Note
 - additionally supports the following runtime option in getImpl():
"validator": an AbstractRestSchemaValidator object for REST message validation (if present, overrides any REST schema validation option provided as a connection option) 
 
- See also
 - BillwerkRestClient::constructor() for more information on the above options