Disallow LDAP bind if trap is set; support setting trap from user form

app/routing/middleware/Traps.middleware.js

@@ -48,6 +48,10 @@ class TrapUtility {
         else if ( this.user ) return this.user.trap
     }
 
+    trap_exists(name) {
+        return !!this.configs[name]
+    }
+
     config() {
         return this.configs[this.get_trap()]
     }