[Feature] Support setting banner on bot profiles (#2879)

src/Discord.Net.Core/Entities/Users/SelfUserProperties.cs

@@ -14,5 +14,10 @@ namespace Discord
         ///     Gets or sets the avatar.
         /// </summary>
         public Optional<Image?> Avatar { get; set; }
+
+        /// <summary>
+        ///     Gets or sets the banner.
+        /// </summary>
+        public Optional<Image?> Banner { get; set; }
     }
 }

src/Discord.Net.Rest/API/Rest/ModifyCurrentUserParams.cs

@@ -9,5 +9,8 @@ namespace Discord.API.Rest
         public Optional<string> Username { get; set; }
         [JsonProperty("avatar")]
         public Optional<Image?> Avatar { get; set; }
+
+        [JsonProperty("banner")]
+        public Optional<Image?> Banner { get; set; }
     }
 }

src/Discord.Net.Rest/Entities/Users/UserHelper.cs

@@ -17,7 +17,8 @@ namespace Discord.Rest
             var apiArgs = new API.Rest.ModifyCurrentUserParams
             {
                 Avatar = args.Avatar.IsSpecified ? args.Avatar.Value?.ToModel() : Optional.Create<ImageModel?>(),
-                Username = args.Username
+                Username = args.Username,
+                Banner = args.Banner.IsSpecified ? args.Banner.Value?.ToModel() : Optional.Create<ImageModel?>()
             };
 
             if (!apiArgs.Avatar.IsSpecified && user.AvatarId != null)