Disable CSRF filter

src/main/java/de/thm/arsnova/config/SecurityConfig.java

@@ -74,6 +74,7 @@ public class SecurityConfig extends WebSecurityConfigurerAdapter {
 	@Override
 	protected void configure(HttpSecurity http) throws Exception {
 		http.exceptionHandling().authenticationEntryPoint(restAuthenticationEntryPoint());
+		http.csrf().disable();
 		http.addFilter(casAuthenticationFilter());
 		http.addFilter(casLogoutFilter());
 		http.addFilterAfter(googleFilter(), CasAuthenticationFilter.class);