Schemas: Add maxNumberOfValues (and if feasible, minNumberOfValues) to each attribute in requiredAttributes and optionalAttributes, and include validation on these values

[reganwolfrom]

NOTE: minNumberOfValues and maxNumberOfValues refers to the number of values, not a number within a single value.

Currently, there is no way to restrict the number of values for an attribute in a schema, i.e., you cannot restrict to only allow a single stringValue or numberValue, nor can you specify "pick at least three of".

Ideally, if there is a minNumberOfValues above the default of 0 or a maxNumberOfValues above the default of 0, validation would be used to ensure the total number of stringValue/stringValues or numberValue/numberValues is within the specific range.

In order to not create conflicting instructions, my recommendation is that there should be no minNumberOfValues=1 accepted, as this would be handled by the attribute being listed as "required"; only 0 or 2+ would be allowed. There would be no such limitation on maxNumberOfValues.

Examples:

When minNumberOfValues=0, maxNumberOfValues=0:
no validation needed

When minNumberOfValues=1,maxNumberOfValues=0:
this setting should be rejected, i.e., should fail to save, as we already use required/optional for this check

When minNumberOfValues=0,maxNumberOfValues=1
this setting prevents numberValues or stringValues from being used; only numberValue and stringValue would be allowed

When minNumberOfValues=2, maxNumberOfValues=1
this setting should be rejected, i.e., should fail to save