Allow multiple weight entries per day

[scrapcode]

Proposed Changes

• Refer to Issue Allow more than one weight entry per day #1814
• Changed the WeightEntry date attribute from a DateField to a DateTimeField
• Removed the unique_together of user and date.
• Removed the restriction of only being allowed to add a new weight entry every so often. You can now add multiple weight entries per day.
  • Removed or altered tests that tested this functionality
• Changed the method of getting and constructing dates from naive to aware, and to include times.
• Added DATETIME_FORMATS constants.
• Modified seeded testing data to reflect aware datetime formats.

TODO: Frontend Implementation

• This will still need implementation on the frontend. Adding multiple weight entries per day works but are currently all added with the time as 23:00:00. How this is displayed on the graph may want to be taken into consideration as well.
  • bug with datepicker for weight measurements flutter#641
  • Update datepicker logic react#990

Please check that the PR fulfills these requirements

• Tests for the changes have been added (for bug fixes / features)
  • Multiple tests and testing methods had to be modified or removed to allow for the new functionality.
• Added yourself to AUTHORS.rst

Other questions

• Do users need to run some commands in their local instances due to this PR
  (e.g. database migration)?

• python manage.py migrate

[rolandgeider]

you're on fire!

Also, there were more changes needed that I had thought. Will you take a shot at the frontend as well or should I do it?

[scrapcode]

Will you take a shot at the frontend as well or should I do it?

I'll give it a whirl!

[rolandgeider]

we can finally merge this 🥳 (and sorry for the wait)

PS: the last test is failing because it can't upload the coverage report, so all is fine