SEC-2690: Support static nested groups in LDAP

This refers to groups that have member: <another group DN> as an attribute
- Add in a utility method in the SpringSecurityLdapTemplate to retrieve multiple attributes and their values from an LDAP record
- Make the DefaultLdapAuthoritiesPopulator more extensible
- Add an LdapAuthority object that holds the DN in addition to other group attributes
- Add a NestedLdapAuthoritiesPopulator to search statically nested groups

ldap/src/test/java/org/springframework/security/ldap/userdetails/LdapAuthorityTests.java

@@ -0,0 +1,52 @@
+package org.springframework.security.ldap.userdetails;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.springframework.security.ldap.SpringSecurityLdapTemplate;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+
+/**
+ * @author Filip Hanik
+ */
+public class LdapAuthorityTests {
+
+    public static final String DN = "cn=filip,ou=Users,dc=test,dc=com";
+    LdapAuthority authority;
+
+    @Before
+    public void setUp() {
+        Map<String,String[]> attributes = new HashMap<String,String[]>();
+        attributes.put(SpringSecurityLdapTemplate.DN_KEY,new String[] {DN});
+        attributes.put("mail",new String[] {"filip@ldap.test.org", "filip@ldap.test2.org"});
+        authority = new LdapAuthority("testRole", DN, attributes);
+    }
+
+    @Test
+    public void testGetDn() throws Exception {
+        assertEquals(DN, authority.getDn());
+        assertNotNull(authority.getAttributeValues(SpringSecurityLdapTemplate.DN_KEY));
+        assertEquals(1, authority.getAttributeValues(SpringSecurityLdapTemplate.DN_KEY).length);
+        assertEquals(DN, authority.getFirstAttributeValue(SpringSecurityLdapTemplate.DN_KEY));
+    }
+
+    @Test
+    public void testGetAttributes() throws Exception {
+        assertNotNull(authority.getAttributes());
+        assertNotNull(authority.getAttributeValues("mail"));
+        assertEquals(2, authority.getAttributeValues("mail").length);
+        assertEquals("filip@ldap.test.org", authority.getFirstAttributeValue("mail"));
+        assertEquals("filip@ldap.test.org", authority.getAttributeValues("mail")[0]);
+        assertEquals("filip@ldap.test2.org", authority.getAttributeValues("mail")[1]);
+    }
+
+    @Test
+    public void testGetAuthority() throws Exception {
+        assertNotNull(authority.getAuthority());
+        assertEquals("testRole",authority.getAuthority());
+    }
+}