A faire en superuser:

-- Revoke privileges from 'public' role
REVOKE CREATE ON SCHEMA public FROM PUBLIC;
REVOKE ALL ON DATABASE mydatabase FROM PUBLIC;

-- Create schema
CREATE SCHEMA myschema

-- Read-only role
CREATE ROLE readonly;
GRANT CONNECT ON DATABASE mydatabase TO readonly;
GRANT USAGE ON SCHEMA myschema TO readonly;
GRANT SELECT ON ALL TABLES IN SCHEMA myschema TO readonly;
ALTER DEFAULT PRIVILEGES IN SCHEMA myschema GRANT SELECT ON TABLES TO readonly;

-- Read/write role
CREATE ROLE readwrite;
GRANT CONNECT ON DATABASE mydatabase TO readwrite;
GRANT USAGE, CREATE ON SCHEMA myschema TO readwrite;
GRANT SELECT, INSERT, UPDATE, DELETE ON ALL TABLES IN SCHEMA myschema TO readwrite;
ALTER DEFAULT PRIVILEGES IN SCHEMA myschema GRANT SELECT, INSERT, UPDATE, DELETE ON TABLES TO readwrite;
GRANT USAGE ON ALL SEQUENCES IN SCHEMA myschema TO readwrite;
ALTER DEFAULT PRIVILEGES IN SCHEMA myschema GRANT USAGE ON SEQUENCES TO readwrite;

-- Users creation
CREATE USER reporting_user1 WITH PASSWORD 'some_secret_passwd';
CREATE USER reporting_user2 WITH PASSWORD 'some_secret_passwd';
CREATE USER app_user1 WITH PASSWORD 'some_secret_passwd';
CREATE USER app_user2 WITH PASSWORD 'some_secret_passwd';

-- Grant privileges to users
GRANT readonly TO reporting_user1;
GRANT readonly TO reporting_user2;
GRANT readwrite TO app_user1;
GRANT readwrite TO app_user2;