Fix base link for issues on group boards

Merged Jarka Košanová requested to merge 3562-issue-links into master

What does this MR do?

It builds a correct link for group boards also in case the group is a subgroup of another group (group.full_path used instead of group.path)

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

The method returned incorrect path for nested groups (the parents were missing in the path)

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

What are the relevant issue numbers?

Closes #3562 (closed)