[FENIX-58] add a script to init user's siteCode with an empty string if the property does not exist

tools/docker/mongo/database_scripts/1.0.0/FENIX-58_init_user_sitecode_ref.js

+db = db.getSiblingDB('iam')
+
+print("START FENIX-58_init_user_sitecode_ref.js");
+
+// Update all users without siteCode : add an empty siteCode
+db.users.updateMany(
+  {"siteCode": {$exists: false}},
+  {
+    $set: {
+      "siteCode": ""
+    }
+  }
+);
+
+print("END FENIX-58_init_user_sitecode_ref.js");