Added the API to remove failed URLs from black list, since now we populate the error code and user can know which URL get blocked

SDWebImage/Core/SDWebImageManager.h

@@ -261,6 +261,17 @@ SDWebImageManager *manager = [SDWebImageManager sharedManager];
  */
 - (void)cancelAll;
 
+/**
+ * Remove the specify URL from failed black list.
+ * @param url The failed URL.
+ */
+- (void)removeFailedURL:(nonnull NSURL *)url;
+
+/**
+ * Remove all the URL from failed black list.
+ */
+- (void)removeAllFailedURLs;
+
 /**
  * Return the cache key for a given URL, does not considerate transformer or thumbnail.
  * @note This method does not have context option, only use the url and manager level cacheKeyFilter to generate the cache key.

SDWebImage/Core/SDWebImageManager.m

@@ -228,6 +228,21 @@ static id<SDImageLoader> _defaultImageLoader;
     return isRunning;
 }
 
+- (void)removeFailedURL:(NSURL *)url {
+    if (!url) {
+        return;
+    }
+    SD_LOCK(self.failedURLsLock);
+    [self.failedURLs removeObject:url];
+    SD_UNLOCK(self.failedURLsLock);
+}
+
+- (void)removeAllFailedURLs {
+    SD_LOCK(self.failedURLsLock);
+    [self.failedURLs removeAllObjects];
+    SD_UNLOCK(self.failedURLsLock);
+}
+
 #pragma mark - Private
 
 // Query normal cache process