Added workaround for duplicate key error

Since we're processing additional data during registration, we need to check if these data were defined in db to be unique. 
For example, email addresses are usually used just once in an application. We can query the database to check if the new email address is not yet registered, but, in some cases, we may more than 2 or 3 or more unique fields (not common, but possible), hence we would also need to query 2,3 or more times. 

As a TEMPORARY WORKAROUND, we'll just attempt to register the new user and wait for the db to throw a DUPLICATE KEY EXCEPTION.

src/Tqdev/PhpCrudApi/Middleware/DbAuthMiddleware.php

@@ -118,7 +118,21 @@ public function process(ServerRequestInterface $request, RequestHandlerInterface
                           }
                       }
                  }
-                $this->db->createSingle($table, $data);
+                try{
+			$this->db->createSingle($table, $data);
+			/* Since we're processing additional data during registration, we need to check if these data were defined in db to be unique. 
+			 * For example, emailAddress are usually used just once in an application. We can query the database to check if the new emailAddress is not yet registered,
+			 * but, in some cases, we may more than 2 or 3 or more unique fields (not common, but possible), hence we would also need to 
+			 * query 2,3 or more times. 
+			 * As a TEMPORARY WORKAROUND, we'll just attempt to register the new user and wait for the db to throw a DUPLICATE KEY EXCEPTION.
+			 */
+		}catch(\PDOException error){
+			if($error->getCode() ==="23000"){
+				return $this->responder->error(ErrorCode::DUPLICATE_KEY_EXCEPTION,'',$error->getMessage());
+			}else{
+				return $this->responder->error(ErrorCode::INPUT_VALIDATION_FAILED,$$error->getMessage());
+			}
+		}
                 $users = $this->db->selectAll($table, $columnNames, $condition, $columnOrdering, 0, 1);
                 foreach ($users as $user) {
                     unset($user[$passwordColumnName]);