Allow donating a message to elementary

[leolost2605]

This would be very useful to investigate issues like #957 or #950 where normal forwarding doesn't work as that just takes the html and builds an entirely new message whereas this only modifies sender and recipient of the original message and sends it as is. For now it gets sent to a throwaway address of mine but it probably would be good to create an account (maybe even an elementary one?) that all contributors have access to (make credentials available in slack?) and change it to that before merging this.
Any feedback regarding design, phrasing or whether this might be problematic in a way would be very appreciated! :)

Below every message:

When the link is clicked:

Fixes #409

[marmeladapk]

Would it be possible to hide that in 3 dot menu for each message? If that line would be added to every message then it would be quite jarring.

TBH, something even better would be an ability to save a complete email into a file (outlook has that option).

[leolost2605]

Would it be possible to hide that in 3 dot menu for each message? If that line would be added to every message then it would be quite jarring.

I agree that this might be annoying when added below every message. My issue with the three dot menu was that I didn't find a good short phrase that would describe what this does (e.g. Donate seemed a bit vague and confusing to me), any ideas?

TBH, something even better would be an ability to save a complete email into a file (outlook has that option).

That sure is possible if we want it and could be implemented additionally. Still I would prefer the way this PR works over having to download the source and then create an issue with that source because the latter just adds a lot more friction. Also with access to the account for donation messages maybe being somewhat limited to elementary contributors this would maybe preserve a little bit more privacy with not everyone being able to just read the messages and mail address.

[wout]

Love the idea!

(e.g. Donate seemed a bit vague and confusing to me), any ideas?

What about Send feedback... to bring it in line with the Feedback app?

[jlnr]

TBH, something even better would be an ability to save a complete email into a file (outlook has that option).

macOS Mail supports message drag and drop as EML files, which can then be compressed and attached to GitHub issues. That also works to attach one message to another one within the mail app. I find that quite elegant, and it also makes it easier to audit the information I'm sending as EML is a plain-text format.