Provide user-defined fields for properties

So a property can have any number of attributes with user-defined values that can be used like custom_codes in all messages.

Like:

• house_door_code

• fence_code

• barrier_code

• floor

• navigation_link

• apartment_number

• parking_spot_number

and any other fields one might need.

Also sometimes multi-linguality is needed / would make sense.

Example house_door_code:

de: [🔔-Taste] 123123 [🔔-Taste]

en: [🔔-Button] 123123 [🔔-Button]

fr: [🔔-Touche] 123123 [🔔-Touche]

if you have many properties you get insane setting all this up with hundreds of custom_codes, never remembering which codes/names existed exactly (you get crazy if you need to click through 20 pages of custom codes to find everything to recreate/copy for this or for that location). And always something is forgotten this way.