Checkout Button Connection

[JakeHamblin]

Description

Created the checkout button connection. When a timesheet is closed, properly update the database and include a response with total time worked.

Issues

Closes #373

Type of change

Select one or more of the following:

• [x] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Other (describe below)

How Has This Been Tested?

• [x] Created event handler
• [x] Created epoch time delta converter
• [x] Opened timesheet
• [x] Waited some time
• [x] Checkout out
• [x] Verified database changed
• [x] Verified expected response

Checklist:

• [x] All local commits have been pushed to remote
• [x] All changes on the base branch have been merged into this branch, either by rebase or merge
• [x] My code is PEP-8 compliant (excluding maximum line length, keep that to 100ish characters)
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have added Google Docstrings for all new functions/methods
• [ ] I have made corresponding changes to the documentation