persist template metadata

init.lua

@@ -1,5 +1,7 @@
 
-pick_and_place = {}
+pick_and_place = {
+	store = minetest.get_mod_storage()
+}
 
 local MP = minetest.get_modpath("pick_and_place")
 dofile(MP .. "/common.lua")

registry.lua

@@ -9,4 +9,19 @@ end
 
 function pick_and_place.get_template(id)
     return registry[id]
-end
+end
+
+local function load()
+    local json = pick_and_place.store:get_string("registry")
+    if json ~= "" then
+        registry = minetest.parse_json(json, {})
+    end
+end
+
+load()
+
+local function save()
+    pick_and_place.store:set_string("registry", minetest.write_json(registry))
+end
+
+minetest.register_on_shutdown(save)