New timecards must be set to their user's organization and business unit

[Jkrzy]

Upon creation, Timecards should have their organization and unit values set to the current values for their associated Employee(UserData)

We have ~2 weeks of timecards which did not have their org and unit values set as expected, they will also need to be remedied.

We'll know we're done when

• Timecards have organization and business unit set on creation
• Timecards organization and business unit are not modified on save
• We have a test case covering this functionality
• We've created a migration or otherwise corrected timecards with no organization/unit set.

[Jkrzy]

Looked into this one a bit -- looks like timecards are being set to their expected org and unit on creation. Unless there's another creation path I'm missing

https://github.com/18F/tock/compare/timecard-creation?expand=1

[Jkrzy]

And on even closer inspection, timecards on production are definitely not having their expected org and unit set on creation. Visible by inspecting Timecards created for 18F folks covering this week's reporting period

[Jkrzy]

We’re using the TimecardForm when timecards are submitted, but not submitting organization/unit with the inbound POST data. Soooooo, we should exclude those fields in the form preventing them from being overwritten.

https://github.com/18F/tock/blob/v20200618.1/tock/hours/forms.py#L39