remove calculations from snake and move it into moves

dbschema/default.esdl

@@ -34,9 +34,10 @@ module default {
       readonly := true;
       on source delete delete target;
     }
-    required single snake: Snake {
+    single snake: Snake {
       readonly := true;
       on source delete delete target;
+      on target delete allow;
     }
   }
 
@@ -47,6 +48,7 @@ module default {
     required is_ladder: bool {
       readonly := true;
     }
+    #constraint exclusive on ( (.name, .is_ladder) );
   }
 
   type Ruleset {
@@ -59,16 +61,13 @@ module default {
     required settings: json {
       readonly := true;
     }
+    #constraint exclusive on ( (.name, .version, .settings) );
   }
 
   type Snake {
     required type: str {
       readonly := true;
     }
-    required multi calculations: Calculations {
-      readonly := true;
-      on source delete delete target;
-    }
   }
 
   type Moves {
@@ -81,12 +80,14 @@ module default {
     required game_board: json {
       readonly := true;
     }
+    single calculations: Calculations {
+      readonly := true;
+      on source delete delete target;
+      on target delete allow;
+    }
   }
 
   type Calculations {
-    required turn: int32 {
-      readonly := true;
-    }
     required data: array<json> {
       readonly := true;
     }