Add UseShopIntegration interface

external/src/main/java/de/epiceric/shopchest/external/UseShopIntegration.java

@@ -0,0 +1,52 @@
+package de.epiceric.shopchest.external;
+
+import org.bukkit.block.Block;
+import org.bukkit.entity.Player;
+
+public interface UseShopIntegration {
+
+    /**
+     * Whether the player can use the player shop represented by this block
+     *
+     * @param block  The {@link Block} where the shop is
+     * @param player The {@link Player} that is trying to use the shop
+     * @return {@code true} if the player can use the shop. {@code false} otherwise
+     */
+    default boolean canUseAdminShop(Block block, Player player) {
+        return true;
+    }
+
+    /**
+     * Whether the player can use the admin shop represented by this block
+     *
+     * @param block  The {@link Block} where the shop is placed
+     * @param player The {@link Player} that is trying to use the shop
+     * @return {@code true} if the player can use the shop. {@code false} otherwise
+     */
+    default boolean canUsePlayerShop(Block block, Player player) {
+        return true;
+    }
+
+    /**
+     * <p>
+     * Whether the player can use the shop represented by this block
+     * </p>
+     * <br>
+     * <p>
+     * It's the method called by the plugin
+     * </p>
+     * <p>
+     * By default, it calls {@link UseShopIntegration#canUsePlayerShop(Block, Player)}} and
+     * {@link UseShopIntegration#canUseAdminShop(Block, Player)}
+     * </p>
+     *
+     * @param block  The {@link Block} where the shop is placed
+     * @param player The {@link Player} that is trying to use the shop
+     * @param admin  Whether this shop is an admin shop
+     * @return {@code true} if the player can use the shop. {@code false} otherwise
+     */
+    default boolean canUseShop(Block block, Player player, boolean admin) {
+        return admin ? canUseAdminShop(block, player) : canUsePlayerShop(block, player);
+    }
+
+}