[keyserver] Return invite links in initial web state

Summary:
When we return initial redux state, we should include invite links which the viewer can use.

The stack contains the implementation of https://linear.app/comm/issue/ENG-3930/accessing-invite-links-non-admin-users-web.

Test Plan: Open web app and check if the links are included in initial redux state.

Reviewers: bartek, kamil, inka, michal

Reviewed By: bartek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D8236