Design Pattern for extensible entity -

i developing application hotel reservation have model called "hotel" has name, description, rate, @ moment want design in way able plugin more simple , complex properties model example address, amenities,

or user model , right have name , lastname user , password , want able add other properties in plugable way .

is there pattern ? builder pattern / observer pattern?

take @ martin fowler's description of dynamic properties (pdf) , user defined fields. can use simple hash table (aka dictionary) hold dynamic properties, depending on language (and implementation) "class schema" won't clear.