The /checkout endpoint should ignore CSRF

If this endpoint is not added to the ignore CSRF list then first time users will get an error when attempting checkout which is not preferrable.
Additionally there is no harm in not having the endpoint CSRF protected as there is no possible harm.

src/main/java/ch/wisv/events/ChConnectConfiguration.java

@@ -81,7 +81,7 @@ public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
                 .csrf(csrf -> csrf
                     .csrfTokenRequestHandler(new XorCsrfTokenRequestAttributeHandler())
                     .csrfTokenRepository(CookieCsrfTokenRepository.withHttpOnlyFalse())
-                    .ignoringRequestMatchers("/api/v1/**")
+                    .ignoringRequestMatchers("/api/v1/**", "/checkout")
                 )
                 .oauth2Login(oauth -> oauth
                     .userInfoEndpoint(userInfo -> userInfo