Add the ability to set the bot banner

src/main/java/net/dv8tion/jda/api/managers/AccountManager.java

@@ -50,6 +50,8 @@ public interface AccountManager extends Manager<AccountManager>
     long NAME        = 1;
     /** Used to reset the avatar field */
     long AVATAR      = 1 << 1;
+    /** Used to reset the banner field */
+    long BANNER      = 1 << 2;
 
     /**
      * The {@link net.dv8tion.jda.api.entities.SelfUser SelfUser} that will be
@@ -137,4 +139,17 @@ public interface AccountManager extends Manager<AccountManager>
     @Nonnull
     @CheckReturnValue
     AccountManager setAvatar(@Nullable Icon avatar);
+
+    /**
+     * Sets the banner for the currently logged in account
+     *
+     * @param  banner
+     *         An {@link net.dv8tion.jda.api.entities.Icon Icon} instance representing
+     *         the new banner for the current account, {@code null} to reset the banner to the default banner.
+     *
+     * @return AccountManager for chaining convenience
+     */
+    @Nonnull
+    @CheckReturnValue
+    AccountManager setBanner(@Nullable Icon banner);
 }

src/main/java/net/dv8tion/jda/internal/managers/AccountManagerImpl.java

@@ -35,6 +35,7 @@ public class AccountManagerImpl extends ManagerBase<AccountManager> implements A
 
     protected String name;
     protected Icon avatar;
+    protected Icon banner;
 
     /**
      * Creates a new AccountManager instance
@@ -63,6 +64,8 @@ public AccountManagerImpl reset(long fields)
         super.reset(fields);
         if ((fields & AVATAR) == AVATAR)
             avatar = null;
+        if ((fields & BANNER) == BANNER)
+            banner = null;
         return this;
     }
 
@@ -110,6 +113,16 @@ public AccountManagerImpl setAvatar(Icon avatar)
         return this;
     }
 
+    @Nonnull
+    @Override
+    @CheckReturnValue
+    public AccountManager setBanner(Icon banner)
+    {
+        this.banner = banner;
+        set |= BANNER;
+        return this;
+    }
+
     @Override
     protected RequestBody finalizeData()
     {
@@ -123,6 +136,8 @@ protected RequestBody finalizeData()
             body.put("username", name);
         if (shouldUpdate(AVATAR))
             body.put("avatar", avatar == null ? null : avatar.getEncoding());
+        if (shouldUpdate(BANNER))
+            body.put("banner", banner == null ? null : banner.getEncoding());
 
         reset();
         return getRequestBody(body);