Initial commit for SendGrid responder

[colin-stubbs]

Adds SendGrid responder to deliver email via SendGrid HTTPS API

[colin-stubbs]

[FR] SendGrid based mail delivery via HTTPS API #738

[dadokkio]

Hi @colin-stubbs , thanks for the pull.
It's working fine and, ignoring some comments in the code, is more or less ok to merge.

Regarding the question you have with thehive:alert support it was created for specific tasks like dataleak. Eg. if you have an alert that creates observable for each mail in a dataleak you could notifies all leaked internal user automatically.
So, probably, your changes that require mail observable starting with "mail:" is not 100% ok.

I've also merged today another pull related to Mailer that enables support for tasks description.

I don't know if you want to review your code or keep the initial release as is.
Probably everyone is going to change details on those responder depending on their necessity in any case.

[jeromeleonard]

Hi @colin-stubbs,

I confirm what @dadokkio said. Mail responders in general can be used for many use cases and custom usages. Depending on incident types, you may store/find recipient email address in tags, CustomFields or observables.