feat: improve meals with better search and ids (#5)

Features:
- Meals now have an id instead of a title only
- It is now possible to get all meals without date or restaurant filter
- Sorting meals output

Reviewed-on: #5
Co-authored-by: bdoerfchen <git@bissendorf.co>
Co-committed-by: bdoerfchen <git@bissendorf.co>

core/handler/params.go

@@ -1,6 +1,6 @@
 package handler
 
 const (
-	ParamDate     string = "date"
-	ParamLocation string = "location"
+	ParamDate       string = "date"
+	ParamRestaurant string = "restaurant"
 )