addEntry:withError: method
   
   
   Adds a new entry cache. 
      Syntax
         
         
            - 
            (
            NSString *
            ) 
            
               addEntry
            
            : 
            (
            ODataEntry *
            ) 
            entry 
            
               withError
            
            : 
            (
            NSError **
            ) 
            error
         
      
      Parameters
         
         
            - 
               entry – 
               locally created entry used to invoke a POST request to the backend.
            
- 
               error – 
               uninitialized error object filled in case of error scenarios.
            
Returns
         string that indicates a temporary entry ID assigned to the locally created entry in cache. 
 id<Caching> cacheLocal = [[Cache alloc] init];
 NSError* error = nil;
 NSString* tempEntryId = [cacheLocal addEntry:entry withError:&error];
 if (error) {
     NSLog("Add Entry Error : %@", error);
     return;
 }