Added the ability to respond to interactions.

Removed the hard coded limit of embeds for webhooks.
Fixed a bug where interactions from DM's throw an error.

javacord-api/src/main/java/org/javacord/api/entity/message/Flag.java

@@ -0,0 +1,55 @@
+package org.javacord.api.entity.message;
+
+/**
+ * Represents a message flag type.
+ */
+public enum Flag {
+
+    /**
+     * An ephemeral message (only visible for the user).
+     */
+    EPHEMERAL(64),
+
+    /**
+     * An unknown flag.
+     */
+    UNKNOWN(-1);
+
+    /**
+     * The id of the flag.
+     */
+    private final int id;
+
+    /**
+     * Creates a new message flag type.
+     *
+     * @param id The id of the type.
+     */
+    Flag(int id) {
+        this.id = id;
+    }
+
+    /**
+     * Gets the id of the message flag type.
+     *
+     * @return The id of the message flag type.
+     */
+    public int getId() {
+        return id;
+    }
+
+    /**
+     * Gets the message flag type by its id.
+     *
+     * @param id The id of the message flag type.
+     * @return The message flag type with the given id or {@link Flag#UNKNOWN} if unknown id.
+     */
+    public static Flag getFlagTypeById(int id) {
+        switch (id) {
+            case 64:
+                return EPHEMERAL;
+            default:
+                return UNKNOWN;
+        }
+    }
+}