feat(zabbixserver): Add Zabbix setup instructions

zabbixserver/build-context/docker-data/postgres/config/docker-entrypoint-initdb.d/init-user-db.sh

@@ -0,0 +1,21 @@
+#!/bin/bash
+set -e
+
+sleep 20
+psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" --dbname "$POSTGRES_DB" <<-EOSQL
+    DO
+        \$block\$
+            BEGIN
+                IF EXISTS (
+                    SELECT FROM pg_catalog.pg_roles WHERE rolname = '${ZBX_DB_USERNAME_RO}'
+                    )
+                THEN
+                    RAISE NOTICE 'Role ''${ZBX_DB_USERNAME_RO}'' already exists. Skipping ...';
+                ELSE
+                    CREATE ROLE "${ZBX_DB_USERNAME_RO}" WITH PASSWORD '${ZBX_DB_USERNAME_PW}';
+                    GRANT CONNECT ON DATABASE "${POSTGRES_DB}" TO "${ZBX_DB_USERNAME_RO}";
+                    GRANT SELECT ON ALL TABLES IN SCHEMA public TO "${ZBX_DB_USERNAME_RO}";
+                END IF;
+            END
+        \$block\$;
+EOSQL