Authenticate when fetching monitors

[tony-pizza]

Adds authentication to the API request that fetches data for individual monitors (via Cronitor::Monitor#data). Currently no authentication is used and this method always returns an Unauthorized response. If an API key is set on the Cronitor::Monitor instance it will be used, otherwise Cronitor.api_key will be used.

Before:

Cronitor::Monitor.new("my-monitor").data
=> #<HTTParty::Response:0x28370 parsed_response={"detail"=>"Authentication credentials were not provided."}, @response=#<Net::HTTPUnauthorized 401 Unauthorized readbody=true>, @headers={"date"=>["Tue, 27 Aug 2024 20:12:07 GMT"], "content-type"=>["application/json"], "content-length"=>["58"], "connection"=>["close"], "server"=>["nginx/1.18.0 (Ubuntu)"], "www-authenticate"=>["bearer"], "vary"=>["Accept, Cookie"], "allow"=>["GET, PUT, DELETE, HEAD, OPTIONS"], "x-frame-options"=>["DENY"]}>

After:

Cronitor::Monitor.new("my-monitor").data
=> #<HTTParty::Response:0x28280 parsed_response={"attributes"=>{...}}, @response=#<Net::HTTPOK 200 OK readbody=true>, @headers={"date"=>["Tue, 27 Aug 2024 19:33:53 GMT"], "content-type"=>["application/json"], "content-length"=>["1159"], "connection"=>["close"], "server"=>["nginx/1.18.0 (Ubuntu)"], "vary"=>["Accept"], "allow"=>["GET, PUT, DELETE, HEAD, OPTIONS"], "x-frame-options"=>["DENY"]}>