[Bug] AddTagToArtifact operation not working in 4.1.3

[androssfox]

Request Type

Bug

Work Environment

Question	Answer
OS version (server)	Ubuntu
OS version (client)	Ubuntu
TheHive version / git hash	4.1.3
Package Type	DEB

Problem Description

Observable responder adding tag to observable no longer working in 4.1.3, it worked before on 4.0.5;

The code at the end of the responder is:

def operations(self, raw):
        return [self.build_operation('AddTagToArtifact', tag='TestTag')]

Steps to Reproduce

1. Run an observable responder that adds a tag to an observable.
2. On version 4.0.5 the tag is added.
3. On version 4.1.3 no tag is added (and no error shows).