feature: import eml files as new tickets

[fiedl]

Sometimes, people who know the support staff in person, won't write emails to the support email address but to the agents' personal email addresses. We've tried really hard, but we can't get these clients to write to the support email address.

This workaround allows to upload email files (*.eml) from the local mail client and to import them as new tickets.

As uploading multiple files is supported, I guess, this can also be used when migrating to brimir in the first place.

How to

Click on "New ticket", then on "import emails".

After importing several emails from the same thread, it might be useful to merge them.

Caveats

• In TicketMailer#receive, I'm setting the created_at column to the email date (https://github.com/ivaldi/brimir/compare/master...fiedl:sf/email-import?expand=1#diff-88f33be098889e6fd2fc29f54e354ab9). If this is undesired, we might need to introduce a sent_at column; but I guess the present solution will do.
• In tickets#show, I needed to change the field, which determines the reply dates, from updated_at to created_at (https://github.com/ivaldi/brimir/commit/905ee91683a77f1848d6880290b7a9beaf64a36d). Otherwise, uploading two emails from yesterday and merging them would show the wrong reply date. I'm not sure why it has been Reply#uploaded_at in the first place, but it might be something to consider.

[coveralls]

Coverage increased (+0.008%) to 92.611% when pulling 905ee91683a77f1848d6880290b7a9beaf64a36d on fiedl:sf/email-import into eb17775b319798fab04031d661933824f57e4e5d on ivaldi:master.

[frenkel]

I used to do this by posting the eml file using curl :rofl:

Another great pull request, thank you! I don't think the caveats matter. It is indeed weird that we used updated_at instead of created_at.

I'm merging it and adding it to the CHANGELOG.md. In the future you may also add it to the CHANGELOG.md yourself if you like.