Update CSRF tests
Update CSRF tests

Adds tests for new CSRF token handling functionality.

  * Tests that GET, HEAD and OPTIONS requests are allowed through
    without a token.
  * Tests that the token can be provided either in the body of the
    request (for example in the case of a POST or PUT request).
  * Tests that the token can be provided in the headers of the request
    (for example in the case of a DELETE or PATCH request).

UKHomeOffice/passports-form-wizard,UKHomeOffice/passports-form-wizard