Allow placeholder `:id` for group link route

What does this MR do?

Part of &4233 (closed)

I am working on converting the group members page from HAML to Vue. As part of this I need access to the group_link resource route on the frontend. Normally in HAML you can do group_group_link_path(group_link) to get the path with the resource ID. In Vue we don't have access to this helper so the easiest way is to pass the path with a placeholder and then replace the placeholder on the frontend.

Example

*.haml

.js-group-linked-list{ data: { member_path: group_group_link_path(id: ':id') } }

*.js

memberPath.replace(/:id$/, member.id)

Conformity

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