Report calculation fails when report start/end have different offset

[lboeman]

If a report's timezone observes DST and the report's start and end fall in standard and daylight time or vice versa, somehwhere along the line the start and end are converted to fixed offset times which raises an exception when slicing. e.g. slicing with start offset -06:00 and end -05:00.

https://sentry.io/organizations/solararbiter-rx/issues/2831552821

[lboeman]

Moved to dashboard as I discovered the issue occurs in the dashboard Javascript and should be converted to UTC before posting here:

solarforecastarbiter-dashboard/sfa_dash/static/js/timerange-handling.js

Line 11 in e682c45

function ParseStartEnd(){

.
This should be handled in the API, by storing the start/end in UTC, but I think it should be consistent.