Turn on Ideas tab after exit survey is displayed

[michael-james]

As a user, after completing the exit survey I want easy access to others' contributions.

Let's discuss implementation on this before starting.

Acceptance criteria:

• add boolean in user table called "shown_survey" that defaults to false
• change "shown_survey" to true when the user goes to the /post route for the first time
• show Ideas tab when "shown_survey" is true for a user
• Change sentence in post to: "You may look at your contributions or visit the Ideas tab above." with Ideas link going to /ideas