use received_at for ingesting emails and feed generation#22

LeonMusCoden merged 2 commits intoLeonMusCoden:masterLeonMusCoden/LetterFeed:masterfrom

invalidusrname:add-received-at-to-entry-and-feed-generatorinvalidusrname/LetterFeed:add-received-at-to-entry-and-feed-generatorCopy head branch name to clipboard