WebHook Reply doesnt work with Fastify Adapter as { content-type': 'application/json'} is missing from headers .

[scyther]

/** fastify web framework */
const fastify: FrameworkAdapter = (req, reply) => ({
    update: Promise.resolve(req.body),
    header: req.headers[SECRET_HEADER_LOWERCASE],
    end: () => reply.status(200).send(),
    respond: (json) => reply.send(json),
    unauthorized: () => reply.code(401).send(WRONG_TOKEN_ERROR),
});

instead of respond: (json) => reply.send(json) it should be respond: (json) => reply.headers({'content-type': 'application/json'}).send(json)

[KnorpelSenf]

I'm surprised that nobody discovered this earlier, thanks for reporting. Could you review #541 and approve it if it is correct?