[ISC-support #22101] Class priority is underdocumented in the ARM

The order in which class information is applied, when defined in multiple classes, is documented only for options (presumed to be both option definitions and option data only by looking at a previous section):

When determining which options to include in the response, the server examines the union of options from all of the assigned classes. If two or more classes include the same option, the value from the first class examined is used; classes are examined in the order they were associated, so ALL is always the first class and matching required classes are last.

It would be nice to extend this to lease lifetimes, v4 fields, and whatever else can be specified as class information.

Also, it would be nice to clarify the relationship of class information relative to global values, shared network values, and subnet values, which is also currently only mentioned for options:

When options are defined as part of the class definition they override any global options that may be defined, and in turn will be overridden by any options defined for an individual subnet.