[Minor] check if type exist

li.strolch.persistence.postgresql/src/main/resources/strolch_db_schema_0.7.0_migration.sql

@@ -1,5 +1,11 @@
 
-CREATE TYPE log_severity_type AS ENUM ('Info', 'Notification', 'Warning', 'Error', 'Exception');
+DO $$
+BEGIN
+    IF NOT EXISTS (SELECT 1 FROM pg_type WHERE typname = 'log_severity_type') THEN
+        CREATE TYPE log_severity_type AS ENUM ('Info', 'Notification', 'Warning', 'Error', 'Exception');
+    END IF;
+END$$;
+
 
 CREATE TABLE IF NOT EXISTS operations_log (
   id varchar(255) PRIMARY KEY,