Fix issue of not being able to delete a task

[aaronw4]

Description

The app was unable to delete tasks. This is because the router delete for user tasks was not adjusted for a postgres database. There was also an issue with an intermediate table not cascading the delete.

Fixes # (issue)
The delete task route was adjusted to find the task by id and then delete. This resulted in an database error because the task id was a foreign key in and intermediate table. The intermediate table was adjusted to cascade the delete on the task.

Type of change

• Bug fix (non-breaking change which fixes an issue)

Change Status

• Complete, tested, ready to review and merge

How Has This Been Tested?

I have a copy of the front-end and back-end in my own repo. I was able to update my own database and test it with the front-end. I was able to create and delete tasks multiple times.

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• My code has been reviewed by at least one peer
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• There are no merge conflicts