Fix readonly user permissions in clickhouse cluster #245
Description
Currently, due to the fact we would like to set things like query priority or maximum query time in the application which is not allowed in readonly mode, we had to use the write user in many places where we would rather not.
We should create a new readonly user that has these permissions and update the following clickhouse URLs to one which has also edit settings permissions: https://clickhouse.com/docs/operations/settings/permissions-for-queries.
The places to update are:
- grafana clickhouse data source
- ooni-api in backend-fsn