Return group information to API

src/constants.rs

@@ -42,5 +42,8 @@ pub const DEFAULT_ACCOUNT_IMAGE: &str = "avatars/0Reverse.png";
 /// The account image to show for users who are not allowed to access other users account images
 pub const ERROR_ACCOUNT_IMAGE: &str = "avatars/0Red.png";
 
+/// The group logo to use when no custom logo have been uploaded
+pub const DEFAULT_GROUP_LOGO: &str = "groups_logo/default.png";
+
 /// Maximum requests size (50 Mo)
 pub const MAX_REQUEST_SIZE: usize = 50000000;