Tear down PermissionError bug fix for Windows OS

[Domejko]

Description

Tear down PermissionError bug fix for Windows OS #173.
Isolated test class ReceiptDownloadEndpointsTest to a separate file test_reciepts_download.py. Changed class inheritance from ViewTestCase to TestCase. Created a tearDownClass classmethod. This changes are made to avoid conflicts between tests while running i parallel on Windows what was causing PermissionError: [Errno 13] The process cannot access the file because it is being used by another process due to the way how Windows is handling the processes.
Added try/except block with info message to catch random occurrences of the error.

Checklist

• Ran the Black Formatter and
  djLint-er on any new code
  (checks
  will
  fail without)
• Made any changes or additions to the documentation where required
• Changes generate no new warnings/errors
• New and existing unit tests pass locally with my
  changes

What type of PR is this?

• 🐛 Bug Fix

Added/updated tests?

• 🙅 no, because they aren't needed

Related PRs, Issues etc

• Related Issue #
• Closes [BUG] Tests fail due to receipt still open when tearing down tests #173

[TreyWW]

Thanks for the contributions recently @Domejko, much appreciated!