Estimated mission duration is wrong

[anetteu]

Describe the bug The estimated duration of missions is clearly not always correct, as seen from the screenshot. I have not checked whether this is caused by a wrong estimation or invalid start/end times.

To Reproduce Start flotilla (on commit cd9a9debf7815c1d648ef3f9d12b384530e2be74 when writing this issue), and have a look at the estimated duration of the missions on the front page.

Expected behavior An reasonable estimated duration of hours.

Screenshots

[oysand]

Change estimates from using end time, it should be estimated duration and calculated in the backend

[GodVenn]

Should be implemented after #554 . Then we need no math in the frontend, but rather to use the "Estimated Duration" field from the mission object.

[Christdej]

554 is implemented