I see attachments can have these link modes:
this.LINK_MODE_IMPORTED_FILE = 0;
this.LINK_MODE_IMPORTED_URL = 1;
this.LINK_MODE_LINKED_FILE = 2;
this.LINK_MODE_LINKED_URL = 3;
What do these link modes mean? I think IMPORTED_FILE means it's in the storage directory, and LINKED_FILE that it lives outside the storage, but I don't know how to interpret this distinction in the case of URLs.
Also, I can't seem to add irc:// urls in the client. Is there a restriction to only ftp:// http:// and https:// schemes?