require 'net/http'
require 'uri'
require 'json'

uri = URI.parse('https://app.tatango.com/api/v2/lists/ID/messages')
http = Net::HTTP.new(uri.host, uri.port)
http.use_ssl = true
request = Net::HTTP::Post.new(uri.request_uri)
request.basic_auth("emailaddress@mydomain.com", "my_api_key")
request['Accept'] = 'application/json'
request['Content-Type'] = 'application/json'
request.body = {"message" => {"content" => "Hello from Tatango!", "send_at" => "2023-12-01T10:00:00Z"}}.to_json
response = http.request(request)

{
  "status": "OK",
  "message": {
    "id": 4
  }
}