Add CSRF example

[devindford]

Description

Add a CSRF example into storedog (for future security products)

How to test

• run docker compose --profile csrf up
• from your favorite place to make requests, send a POST request to 127.0.0.1:7578 with a body of username=devin.ford@datadoghq.com&password=test123 and a Content-Type of application/x-www-form-urlencoded
• you should receive a response that you are logged in
• you will also receive a session cookie, you will need this to logout
• send a GET request to 127.0.0.1:7578/logout and you should get a response of logged out

Checklist

Before you move on, make sure that:

• No unintended changes are included
• Spelling is correct
• There are tests covering new/changed functionality
• Commits have meaningful names and changes. CR remarks-like commits are squashed.
• Proper labels assigned. Use WIP label to indicate that state