Implement shop purchase limits

src/main/java/emu/nebula/database/DatabaseManager.java

@@ -64,7 +64,8 @@ public final class DatabaseManager {
         
         // Add our custom fastutil codecs
         var codecProvider = CodecRegistries.fromCodecs(
-               new IntSetCodec(), new IntListCodec(), new Int2IntMapCodec(), new ItemParamMapCodec(), new BitsetCodec()
+               new IntSetCodec(), new IntListCodec(), new Int2IntMapCodec(),
+               new ItemParamMapCodec(), new String2IntMapCodec(), new BitsetCodec()
         );
 
         // Set mapper options

src/main/java/emu/nebula/database/codecs/String2IntMapCodec.java

@@ -0,0 +1,42 @@
+package emu.nebula.database.codecs;
+
+import org.bson.BsonReader;
+import org.bson.BsonType;
+import org.bson.BsonWriter;
+import org.bson.codecs.Codec;
+import org.bson.codecs.DecoderContext;
+import org.bson.codecs.EncoderContext;
+
+import emu.nebula.util.String2IntMap;
+
+/**
+ * Custom mongodb codec for encoding/decoding fastutil int2int maps.
+ */
+public class String2IntMapCodec implements Codec<String2IntMap> {
+
+    @Override
+    public Class<String2IntMap> getEncoderClass() {
+        return String2IntMap.class;
+    }
+
+    @Override
+    public void encode(BsonWriter writer, String2IntMap collection, EncoderContext encoderContext) {
+        writer.writeStartDocument();
+        for (var entry : collection.object2IntEntrySet()) {
+            writer.writeName(entry.getKey());
+            writer.writeInt32(entry.getIntValue());
+        }
+        writer.writeEndDocument();
+    }
+
+    @Override
+    public String2IntMap decode(BsonReader reader, DecoderContext decoderContext) {
+        String2IntMap collection = new String2IntMap();
+        reader.readStartDocument();
+        while (reader.readBsonType() != BsonType.END_OF_DOCUMENT) {
+            collection.put(reader.readName(), reader.readInt32());
+        }
+        reader.readEndDocument();
+        return collection;
+    }
+}