add common interface for interactions with a custom ID

src/main/java/net/dv8tion/jda/api/interactions/CustomIdInteraction.java

@@ -0,0 +1,29 @@
+package net.dv8tion.jda.api.interactions;
+
+import net.dv8tion.jda.api.interactions.components.ComponentInteraction;
+import net.dv8tion.jda.api.interactions.modals.ModalInteraction;
+
+import javax.annotation.Nonnull;
+
+/**
+ * Interactions which have a custom ID, namely {@link ComponentInteraction} and {@link  ModalInteraction}.
+ *
+ * <br>This id does not have to be numerical.
+ *
+ */
+public interface CustomIdInteraction
+{
+    /**
+     * The custom ID provided to the component or modal when it was originally created.
+     * <br>This value should be used to determine what action to take in regard to this interaction.
+     *
+     * <br>This id does not have to be numerical.
+     *
+     * @return The custom ID
+     *
+     * @see ComponentInteraction#getComponentId()
+     * @see ModalInteraction#getModalId()
+     */
+    @Nonnull
+    String getCustomId();
+}

src/main/java/net/dv8tion/jda/api/interactions/components/ComponentInteraction.java

@@ -19,6 +19,7 @@
 import net.dv8tion.jda.api.entities.Message;
 import net.dv8tion.jda.api.entities.channel.unions.GuildMessageChannelUnion;
 import net.dv8tion.jda.api.entities.channel.unions.MessageChannelUnion;
+import net.dv8tion.jda.api.interactions.CustomIdInteraction;
 import net.dv8tion.jda.api.interactions.callbacks.IMessageEditCallback;
 import net.dv8tion.jda.api.interactions.callbacks.IModalCallback;
 import net.dv8tion.jda.api.interactions.callbacks.IPremiumRequiredReplyCallback;
@@ -32,8 +33,16 @@
  * <p>Instead of {@link #deferReply()} and {@link #reply(String)} you can use {@link #deferEdit()} and {@link #editMessage(String)} with these interactions!
  * <b>You can only acknowledge an interaction once!</b>
  */
-public interface ComponentInteraction extends IReplyCallback, IMessageEditCallback, IModalCallback, IPremiumRequiredReplyCallback
+public interface ComponentInteraction extends IReplyCallback, IMessageEditCallback, IModalCallback, IPremiumRequiredReplyCallback, CustomIdInteraction
 {
+
+    @Override
+    @Nonnull
+    default String getCustomId()
+    {
+        return getComponentId();
+    }
+
     /**
      * The custom component ID provided to the component when it was originally created.
      * <br>This value should be used to determine what action to take in regard to this interaction.

src/main/java/net/dv8tion/jda/api/interactions/modals/ModalInteraction.java

@@ -19,9 +19,11 @@
 import net.dv8tion.jda.api.entities.Message;
 import net.dv8tion.jda.api.entities.channel.unions.GuildMessageChannelUnion;
 import net.dv8tion.jda.api.entities.channel.unions.MessageChannelUnion;
+import net.dv8tion.jda.api.interactions.CustomIdInteraction;
 import net.dv8tion.jda.api.interactions.callbacks.IMessageEditCallback;
 import net.dv8tion.jda.api.interactions.callbacks.IReplyCallback;
 import net.dv8tion.jda.internal.utils.Checks;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Unmodifiable;
 
 import javax.annotation.Nonnull;
@@ -36,8 +38,16 @@
  *
  * @see    net.dv8tion.jda.api.events.interaction.ModalInteractionEvent
  */
-public interface ModalInteraction extends IReplyCallback, IMessageEditCallback
+public interface ModalInteraction extends IReplyCallback, IMessageEditCallback, CustomIdInteraction
 {
+
+    @Override
+    @NotNull
+    default String getCustomId()
+    {
+        return getModalId();
+    }
+
     /**
      * Returns the custom id of the Modal in question
      *