SparkPostTransport features a hardcoded endpoint for a service that has multiple endpoints

[Raven0us]

In /src/Illuminate/Mail/Transport/SparkPostTransport.php under the method send, the endpoint is hardcoded to https://api.sparkpost.com/api/v1/transmissions.

This should be configurable when setting up SparkPost as the app's mail driver because SparkPost has 4 different endpoints, according to https://developers.sparkpost.com/api/

In my case, it was not about alternative endpoints, but very strict endpoints. SparkPost and SparkPost EU operate independently, that means if I create an API key for SparkPost EU and try to use it in Laravel, it won't work cause the generic endpoint is called instead of https://api.eu.sparkpost.com/api/v1 (where my API key actually exists).

I solved this by extending MailServiceProvider, TransportManager and SparkPostTransport, but that's not a solution.