mapper-attachments - copy_to doesn't work

[chindhuhari]

Elasticsearch version: 2.3.2

Plugins installed: [mapper-attachments]

JVM version: 1.8

OS version: Windows

Description of the problem including expected versus actual behavior:

Steps to reproduce:
Similar to elastic/elasticsearch-mapper-attachments#216 and #14946
We couldn't find as to in which version this was fixed.
If there is a document or references available, please do help us with the links leading to it

Provide logs (if relevant):

Describe the feature:

[SKumarMN]

I am facing the same issue too. Can you please let know if there is a fix if so in which version or this feature(copy_to in subfields) is not supported at all

[dadoonet]

Duplicate of #18361.