feat(TextBasedChannel): add lastPinTimestamp and lastPinAt (#2813)

* add lastPinTimestamp

* typings

* use or instead of ternary

src/structures/DMChannel.js

@@ -32,6 +32,12 @@ class DMChannel extends Channel {
      * @type {?Snowflake}
      */
     this.lastMessageID = data.last_message_id;
+
+    /**
+     * The timestamp when the last pinned message was pinned, if there was one
+     * @type {?number}
+     */
+    this.lastPinTimestamp = data.last_pin_timestamp ? new Date(data.last_pin_timestamp).getTime() : null;
   }
 
   /**
@@ -49,6 +55,7 @@ class DMChannel extends Channel {
   // These are here only for documentation purposes - they are implemented by TextBasedChannel
   /* eslint-disable no-empty-function */
   get lastMessage() {}
+  get lastPinAt() {}
   send() {}
   search() {}
   startTyping() {}

src/structures/GroupDMChannel.js

@@ -103,6 +103,12 @@ class GroupDMChannel extends Channel {
      * @type {?Snowflake}
      */
     this.lastMessageID = data.last_message_id;
+
+    /**
+     * The timestamp when the last pinned message was pinned, if there was one
+     * @type {?number}
+     */
+    this.lastPinTimestamp = data.last_pin_timestamp ? new Date(data.last_pin_timestamp).getTime() : null;
   }
 
   /**
@@ -219,6 +225,7 @@ class GroupDMChannel extends Channel {
   // These are here only for documentation purposes - they are implemented by TextBasedChannel
   /* eslint-disable no-empty-function */
   get lastMessage() {}
+  get lastPinAt() {}
   send() {}
   search() {}
   startTyping() {}

src/structures/TextChannel.js

@@ -43,6 +43,12 @@ class TextChannel extends GuildChannel {
      */
     this.lastMessageID = data.last_message_id;
 
+    /**
+     * The timestamp when the last pinned message was pinned, if there was one
+     * @type {?number}
+     */
+    this.lastPinTimestamp = data.last_pin_timestamp ? new Date(data.last_pin_timestamp).getTime() : null;
+
     if (data.messages) for (const message of data.messages) this.messages.add(message);
   }
 
@@ -101,6 +107,7 @@ class TextChannel extends GuildChannel {
   // These are here only for documentation purposes - they are implemented by TextBasedChannel
   /* eslint-disable no-empty-function */
   get lastMessage() {}
+  get lastPinAt() {}
   send() {}
   search() {}
   startTyping() {}

src/structures/interfaces/TextBasedChannel.js

@@ -21,6 +21,12 @@ class TextBasedChannel {
      * @type {?Snowflake}
      */
     this.lastMessageID = null;
+
+    /**
+     * The timestamp when the last pinned message was pinned, if there was one
+     * @type {?number}
+     */
+    this.lastPinTimestamp = null;
   }
 
   /**
@@ -32,6 +38,15 @@ class TextBasedChannel {
     return this.messages.get(this.lastMessageID) || null;
   }
 
+  /**
+   * The date when the last pinned message was pinned, if there was one
+   * @type {?Date}
+   * @readonly
+   */
+  get lastPinAt() {
+    return this.lastPinTimestamp ? new Date(this.lastPinTimestamp) : null;
+  }
+
   /**
    * Options provided when sending or editing a message.
    * @typedef {Object} MessageOptions
@@ -322,6 +337,7 @@ class TextBasedChannel {
     if (full) {
       props.push(
         'lastMessage',
+        'lastPinAt',
         'bulkDelete',
         'startTyping',
         'stopTyping',