Webhook Test Deliveries

[yoyostile]

The customer needs a way to generate webook test deliveries via API. Our documentation states we would send a new Webhook on each callback_url change, which is wrong.
Also re-triggering of failed webhooks (e.g. a makerist problem, as their backend is broken all the time :)) should be possible via API.

We need to improve on our documentation for webhooks. Especially HMAC in the webhook http header should be described. What kind of algorithm are we using for integrity checks? How to verify the HMAC? etc.

[bumi]

is there already some interface that lists stuff like the delivered webhooks? something like github has for their webhooks?

[bumi]

as the webhooks are a core function of the box I'd say this is rather important.
The user must be able to trust the webhooks, no webhooks must be lost and it should be super transparent to the user what requests have been sent or not sent.

[bumi]

closing in favor of: #139 #138 #137