Firing a Signed Webhook Request

[gja]

There is no way to use this library currently to trigger a web hook to start a flow with message bird. Here is the code I'm using for this. I'll try to open a PR incorporating this sometime in the future.

module MessageBirdWebhook
 def self.build_payload(time, body)
 parts = []
 parts.push(time)
 parts.push("")
 parts.push(Digest::SHA256.new.digest(body))
 parts.join("\n")
 end

 def self.sign_webhook_request(signing_key, body, now = Time.now)
 now = now.getutc.to_i
 signature = OpenSSL::HMAC.digest(OpenSSL::Digest.new('sha256'), signing_key, build_payload(now, body))

 {
 "MessageBird-Request-Timestamp" => now.to_s,
 "MessageBird-Signature" => Base64.encode64(signature).strip,
 }
 end

 def self.trigger_webhook(signing_key, webhook_id, params)
 body = params.to_json
 client = Faraday.new(url: "https://flows.messagebird.com", headers: { 'Content-Type' => 'application/json' })
 client.post("/flows/#{webhook_id}/invoke", body, sign_webhook_request(signing_key, body))
 end
end