Add support for special characters used in attachment field when importing attachment using CSV

Problem Definition

We can import attachments with following the instruction described in How to import attachment using CSV. (I confirmed that the solution still works on JIRA 7.4.1.)

Currently, JIRA doesn't allow us to use special characters like "#", ",", "[" used in attachment field. (e.g. file://csvimport/test#test.txt) We can attach files which are using such special characters in the file names from the UI.
The way to escape special characters is described in Treating special characters literally but it doesn't work in this case.

Suggested Solution

It would be better if we could use such special characters in attachment field even when importing attachment using CSV.

Workaround

Replace the special characters manually as per its URL encoding, refer to https://www.w3schools.com/tags/ref_urlencode.asp