Make library database publicly readable

[akdasa]

Implementation plan:

Update migration script to:

1. Remove _admin role from the members group from library database.
2. Add _design/permissions document with validate_doc_update function to the library database to check if user has one of the following roles: _admin, contentManager.

Acceptance criteria:

1. User should not be able to create new documents:

   curl -X POST http://localhost:5984/library \
    -H "Content-Type: application/json" \
    -d '{"title": "Example Book", "author": "John Doe", "year": 2023}'

2. User should be able to access documents

   curl -X GET http://database:5984/library/_all_docs

3. Admin should be able to create documents via CouchDB admin panel

Related docs:

1. https://docs.couchdb.org/en/stable/api/database/security.html#put--db-_security

[akdasa]

Updated migration script. Will be applied to PROD once we start public alpha testing.