Add MembersLogin delegate, for external log in

Usign a section that does not contains a password has been discussed in
issue #274, but the PR did not actually provide a way to let other
extension authenticate the user.

Only if the members section DOES BOT contains a password field, the new
MembersLogin will be called. By default, log in is refused and extension
must explicitly set the required parameters with good values for the
login to succeed.

lib/member.symphony.php

@@ -64,31 +64,66 @@ public function setIdentityField(array $credentials, $simplified = true) {
 		 * @return integer
 		 */
 		public function findMemberIDFromCredentials(array $credentials, $isHashed = false) {
-			if((
-				(!isset($credentials['username']) || is_null($credentials['username']))
-				&& (!isset($credentials['email']) || is_null($credentials['email']))
-			)) {
+			if(empty($credentials['username']) && empty($credentials['email'])) {
 				return null;
 			}
 
 			$identity = $this->setIdentityField($credentials);
-
-			if(!$identity instanceof Field) return null;
+			if(!($identity instanceof Field)) {
+				return null;
+			}
 
 			// Member from Identity
 			$member_id = $identity->fetchMemberIDBy($credentials);
 
 			// Validate against Password
 			$auth = $this->section->getField('authentication');
-			if(!is_null($auth)) {
+			if($auth instanceof Field) {
 				$member_id = $auth->fetchMemberIDBy($credentials, $member_id, $isHashed);
+			} else {
+				// No authentication field defined, let extensions try
+				$isLoggedIn = false;
+				/**
+				 * Fired when no authentication field is present.
+				 * Never fired if the Members section contains an authentication field.
+				 * Allow extensions to define their own auth mechanism for password less login.
+				 *
+				 * @delegate MembersLogin
+				 * @since members 1.9.0
+				 * @param string $context
+				 *  '/frontend/'
+				 * @param boolean is-logged-in
+				 *  If the current login is valid or not.
+				 *  Extensions are expected to update this value.
+				 * @param SymphonyMember $driver
+				 *  The SymphonyMember driver
+				 * @param array $credentials
+				 *  The credentials value
+				 * @param int $member_id
+				 *  The member_id found for this credentials
+				 *  Extensions are expected to update this value.
+				 * @param array $errors
+				 *  The error array
+				 */
+				Symphony::ExtensionManager()->notifyMembers('MembersLogin', '/frontend/', array(
+					'is-logged-in' => &$isLoggedIn,
+					'driver' => $this,
+					'credentials' => $credentials,
+					'member_id' => &$member_id,
+					'errors' => &extension_Members::$_errors,
+				));
+				if (!$isLoggedIn) {
+					$member_id = null;
+				}
 			}
 
 			// No Member found, can't even begin to check Activation
 			// Return null
-			if(is_null($member_id)) return null;
+			if(!$member_id) {
+				return null;
+			}
 
-			// Check that if there's activiation, that this Member is activated.
+			// Check that if there's activation, that this Member is activated.
 			if(!is_null($this->section->getFieldHandle('activation'))) {
 				$entry = EntryManager::fetch($member_id, NULL, NULL, NULL, NULL, NULL, false, true, array($this->section->getFieldHandle('activation')));
 
@@ -222,7 +257,6 @@ public function login(array $credentials, $isHashed = false) {
 					'type' => 'invalid',
 					'label' => $this->section->getField('email')->get('label')
 				);
-				return null;
 			}
 
 			// If there is errors already, no point continuing, return false