Add support for sendgrid template engine.

[tant42]

Added support for sendgrid template engine by allowing us to enable it and adding a function to set the template_id.

Remove redundant json dependency from gemspec.

[nesrual]

+1 really useful

[Isildy]

Can you give an example of how to use it?

[abhchand]

Is there an update on this? It's been open for over a year now and is a pretty core part of the API.

Also several people are migrating over from Mandrill to SendGrid given the recent news with Mandrill/MailChimp, so this is a critical requirement for newcomers. Not having the template feature available is definite deal breaker for those of us who store all our email templates vendor-side.

As for the requested example - the author should definitely be on the hook for filling out a description and example, but in this particular case the usage is almost identical to the other X-SMTPAPI functionality this gem provides.

It's also worth noting that there's been an almost identical PR to add this same functionality open for even longer, since 2014: #19

Thanks.

[LaurMo]

+1 @abhchand

[abhchand]

Typo - should be @sg_template_id everywhere in this file

[Intrepidd]

👍 Would love to see that

[tant42]

Pull request has been updated with test to demonstrate usage. (Basically in the mailer function you need to call:

  sendgrid_enable :templates
  sendgrid_template_id <the template uuid>

Use sendgrid_substitute to provide template values.

There's also a bit that's undocumented, but the only way I could get a template item to send correctly is with set the mail options "to" to "[email protected]" and use sendgrid_recipients to set who the emails send to. Otherwise, "to" person is set as the recipient for all people in the sendgrid_recipients list (at least when I first implemented this. That might have been fixed by now).

[gkunwar]

@tant42 I really need this feature, how can I use this?

[tant42]

Anything else I need to fix before this can be merged?