Default permissions don't allow the Open Social GraphQL endpoint to be used

Problem/Motivation

By default users don't get the "execute arbitrary query" permission on GraphQL servers, but this is basically what every GraphQL application does.

Since we rely on the default user permissions (and OAuth scopes for applications in the future) we at least require the endpoint itself to be accessible.

Steps to reproduce

Proposed resolution

Provide the execute open_social_graphql arbitrary graphql requests permission to anonymous and authenticated users.

Remaining tasks

User interface changes

API changes

Data model changes