Move custom filter examples (#1465)

* Move custom filter examples

* Remove unused README entry

spring-security-rest-basic-auth/src/main/java/org/baeldung/filter/CustomFilter.java

@@ -0,0 +1,18 @@
+package org.baeldung.filter;
+
+import org.springframework.web.filter.GenericFilterBean;
+
+import javax.servlet.FilterChain;
+import javax.servlet.ServletException;
+import javax.servlet.ServletRequest;
+import javax.servlet.ServletResponse;
+import java.io.IOException;
+
+public class CustomFilter extends GenericFilterBean {
+
+    @Override
+    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
+        chain.doFilter(request, response);
+    }
+
+}

spring-security-rest-basic-auth/src/main/java/org/baeldung/filter/CustomWebSecurityConfigurerAdapter.java

@@ -0,0 +1,41 @@
+package org.baeldung.filter;
+
+import org.baeldung.security.RestAuthenticationEntryPoint;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder;
+import org.springframework.security.config.annotation.web.builders.HttpSecurity;
+import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
+import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
+import org.springframework.security.web.authentication.www.BasicAuthenticationFilter;
+
+@Configuration
+@EnableWebSecurity
+public class CustomWebSecurityConfigurerAdapter extends WebSecurityConfigurerAdapter {
+
+    @Autowired private RestAuthenticationEntryPoint authenticationEntryPoint;
+
+    @Autowired
+    public void configureGlobal(AuthenticationManagerBuilder auth) throws Exception {
+        auth
+          .inMemoryAuthentication()
+          .withUser("user1")
+          .password("user1Pass")
+          .authorities("ROLE_USER");
+    }
+
+    @Override
+    protected void configure(HttpSecurity http) throws Exception {
+        http
+          .authorizeRequests()
+          .antMatchers("/securityNone")
+          .permitAll()
+          .anyRequest()
+          .authenticated()
+          .and()
+          .httpBasic()
+          .authenticationEntryPoint(authenticationEntryPoint);
+
+        http.addFilterAfter(new CustomFilter(), BasicAuthenticationFilter.class);
+    }
+}