[511] User activity on Phoenix app resets the Rails session timeout

[cpreisinger]

Description

Work in progress towards 511. Placed on hold at the end of development.

Related Issues

GSA/Challenge_platform#511

Changes Made

• [List the specific changes made in bullet points.]

Screenshots (if applicable)

[Include screenshots to visually demonstrate changes, if relevant.]

Checklist

• PR is assigned to a project: Challenge_gov Board
• PR is assigned to a milestone: current sprint
• GH issues are assigned to the PR (under Development section on the right hand side)
• PR is assigned a reviewer, and requires code review and approval by a teammate
• New functionality is tested and all tests are green
• I have added unit tests for new functionality or updated existing tests for changes.
• I have updated the documentation/README accordingly, if necessary.
• If you have DB migration, it is a "safe" migration and you've confirmed it can be rolled back.
• If applicable, Controllers modified contain appropriate authorization plugs
• This PR has been reviewed by at least one other team member.
• Build has been approved for deployment in CircleCI.