Add mail template param

[MarkBarbieri]

Proposing the following to allow complex/custom html or text email templates.

May be an alternate solution to #2541

This allows for a complete custom template to be defined and referenced in the EmailAgent options

[dsander]

Thank you for your contribution @MarkBarbieri!

I don't think that is a good solution, users should not need to put files on the server Huginn runs on to use templates. credentials could be an option that works for users with different installation methods like docker

[MarkBarbieri]

credentials could be an option that works for users with different installation methods like docker

I'd like to know more about how this would work to solve my problem. This proposed change isn't about supporting different installation methods, it's to provide an option for more richly formatted messages, for example, custom css, etc.

I'm using Huginn for monitoring rss feeds, etc, and some of the content from the feed does not format well, so I want to provide custom css in the header, with a custom footer. I don't want to sanitize the body, which is forced in the current template.

This might be a little bespoke, but seems useful to me and for what I've been doing, it's worked fantastically without disrupting any other normal use.

[MarkBarbieri]

Thank you for your contribution @MarkBarbieri!

I don't think that is a good solution, users should not need to put files on the server Huginn runs on to use templates. credentials could be an option that works for users with different installation methods like docker

@dsander It's been a long time coming, but I've updated this PR so that the template can be defined inline using credentials. It is no longer required to put files on the server