Add some code comments, update BungeeCord version check

bootstrap/bungeecord/src/main/java/org/geysermc/geyser/platform/bungeecord/GeyserBungeePlugin.java

@@ -83,7 +83,7 @@ public class GeyserBungeePlugin extends Plugin implements GeyserBootstrap {
         // Copied from ViaVersion.
         // https://github.com/ViaVersion/ViaVersion/blob/b8072aad86695cc8ec6f5e4103e43baf3abf6cc5/bungee/src/main/java/us/myles/ViaVersion/BungeePlugin.java#L43
         try {
-            ProtocolConstants.class.getField("MINECRAFT_1_21");
+            ProtocolConstants.class.getField("MINECRAFT_1_21_4");
         } catch (NoSuchFieldException e) {
             geyserLogger.error("      / \\");
             geyserLogger.error("     /   \\");

core/src/main/java/org/geysermc/geyser/entity/type/living/animal/tameable/WolfEntity.java

@@ -128,6 +128,7 @@ public class WolfEntity extends TameableEntity {
     public void setBody(ItemStack stack) {
         super.setBody(stack);
         isCurseOfBinding = ItemUtils.hasEffect(session, stack, EnchantmentComponent.PREVENT_ARMOR_CHANGE);
+        // Not using ItemStack#getDataComponents as that wouldn't include default item components
         repairableItems = GeyserItemStack.from(stack).getComponent(DataComponentType.REPAIRABLE);
     }
 

core/src/main/java/org/geysermc/geyser/inventory/GeyserItemStack.java

@@ -125,6 +125,10 @@ public class GeyserItemStack {
         return isEmpty() ? null : components;
     }
 
+    /**
+     * @return whether this GeyserItemStack has any additional components on top of
+     * the base item components.
+     */
     public boolean hasNonBaseComponents() {
         return components != null;
     }
@@ -137,6 +141,15 @@ public class GeyserItemStack {
         return components;
     }
 
+    /**
+     * Returns the stored data component for a given {@link DataComponentType}, or null.
+     * <p>
+     * This method will first check the additional components that may exist,
+     * and fallback to the item's default (or, "base") components if need be.
+     * @param type the {@link DataComponentType} to query
+     * @return the value for said type, or null.
+     * @param <T> the value's type
+     */
     @Nullable
     public <T> T getComponent(@NonNull DataComponentType<T> type) {
         if (components == null) {

core/src/main/java/org/geysermc/geyser/item/type/Item.java

@@ -100,21 +100,33 @@ public class Item {
     }
 
     /**
-     * Returns a modifiable DataComponents map. Should only be used when it must be modified.
+     * Returns an unmodifiable {@link DataComponents} view containing known data components.
-     * Otherwise, prefer using GeyserItemStack's getComponent
+     * Optionally, additional components can be provided to replace (or add to)
+     * the items' base components.
+     * To add data components, use {@link GeyserItemStack#getOrCreateComponents()}.
      */
     @NonNull
     @UnmodifiableView
-    public DataComponents gatherComponents(DataComponents others) {
+    public DataComponents gatherComponents(@Nullable DataComponents others) {
         if (others == null) {
             return baseComponents;
         }
 
+        // Start with the base components that always exist
         DataComponents components = baseComponents.clone();
+        // Add all additional components; these can override base components!
+        // e.g. custom stack size
         components.getDataComponents().putAll(others.getDataComponents());
+
+        // Return an unmodified map of the merged components
         return new DataComponents(ImmutableMap.copyOf(components.getDataComponents()));
     }
 
+    /**
+     * Returns this items value (or null) for a specific {@link DataComponentType}.
+     * Prefer using {@link GeyserItemStack#getComponent(DataComponentType)}
+     * to also query additional components that would override the default ones.
+     */
     @Nullable
     public <T> T getComponent(@NonNull DataComponentType<T> type) {
         return baseComponents.get(type);