Create a PUT route to update a users assessment with evidence in the DB

[chrislaupama]

Our users will be wanting to submit evidence that they've completed an assessment. Create a PUT route which allows them to do so.

Tasks:

• [ ] Refer to the wiki to see how the routes may need to be setup.
• [ ] Create route.
• [ ] Create db function.
• [ ] Write tests for this route.
• [ ] Write tests for db function.

[paul-renwick]

Estimated time 2 hours.