add client4 apis needed for jira plugin (#7292)

i18n/en.json

@@ -5103,6 +5103,10 @@
     "id": "model.utils.decode_json.app_error",
     "translation": "could not decode"
   },
+  {
+    "id": "plugin.rpcplugin.invocation.error",
+    "translation": "Error invoking plugin RPC"
+  },
   {
     "id": "store.sql.alter_column_type.critical",
     "translation": "Failed to alter column type %v"