allow upload of mission summary/notes on completion

[staceysv]

When a crew completes a mission, we ask the captain to give us a quick review (e.g. of how the mission went, highs/lows, what was the best part) and a photo that we can save as the final report on the mission (default: a celebratory GIF or nature photo). We can show this photo & review when referencing this completed mission and store the accumulating reviews as a scrapbook/way for crews to see their collective journey.