Add +sharedInstance for A0Lock

Pod/Classes/Core/A0Lock.h

@@ -117,6 +117,17 @@ NS_ASSUME_NONNULL_BEGIN
  */
 + (instancetype)newLock;
 
+/**
+ *  Returns a shared instance of Lock with credentials obtained from Info.plist.
+ *  These are the the valid entries:
+ *      - Auth0ClientId: Your app's client identifier in Auth0.
+ *      - Auth0Domain: Your app's domain name or url in Auth0. e.g: samples.auth0.com or https://samples.auth0.com
+ *      - Auth0ConfigurationDomain: Your app's configuration domain name or url where we get yout app configuration. This value is optional and will default to Auth0 CDN.
+ *
+ *  @return a shared instance
+ */
++ (instancetype)sharedLock;
+
 /**
  *  Auth0 Authentication API client.
  *

Pod/Classes/Core/A0Lock.m

@@ -107,6 +107,15 @@ - (instancetype)initWithClientId:(NSString *)clientId domain:(NSString *)domain
     return self;
 }
 
++ (instancetype)sharedLock {
+    static A0Lock *SharedInstance;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        SharedInstance = [A0Lock newLock];
+    });
+    return SharedInstance;
+}
+
 - (A0APIClient *)apiClient {
     return self.client;
 }