Frontend: Add channel access granting/revoking support

database_settings.sql

@@ -16,7 +16,6 @@ create table servers(id int primary key not null,
 	port int not null
 );
 
-create table accessors(id int primary key not null,
-	channel_id int not null, -- foreign key in channels table
-	user_id int not null -- foreign key in users table
+create table accessors(user_id int not null, -- foreign key in users table
+	channel_id int not null -- foreign key in channels table
 );