Defines a dispatch method for the the endpoint with `endpoint-name`.

In the parameter declarations `[major-var & params]`, the major variable always comes first,
no matter at which position it is in the actual endpoint definition.
Even if the corresponding endpoint does not have a major variable,
a symbol for it needs to be provided in the parameters (typically `_` since it will always be bound to `nil`).

`opts` are the optional parameters as specified in the endpoint definition,
`method` is the http method used (`:get`, `:post`, ...),
`status-sym` is a symbol that will be bound to the response code (http status),
`body-sym` is a symbol that will be bound to the response body (as a string),
`url-string` is the url of the endpoint (its expression can depend on the arguments),
`method-params` is a map describing what to send in the request,
`promise-val` is the expression that will be in the promise returned to the user of the endpoint.

Takes a process and endpoint, and dispatches an http request.
Must return the response object from the call to allow the runtime
to update the rate limit.

Makes a request after waiting for the rate limit, retrying if necessary.

Returns the number of millis until the limit expires, or nil if not limited

Takes a token for a bot and returns a channel to communicate with the
message sending process.

Takes a process and an event, and runs the request, respecting rate limits

Takes the channel returned from start! and stops the messaging process.

Takes a rate-limit and a map of headers and returns an updated rate-limit.

If rate limit headers are included in the map, then the rate limit is updated
to them, otherwise the existing rate limit is used, but the remaining limit is
decremented.