use case:
"suggested values" are primarily used with parameters that are fed into {{#switch "template condition".
in actual usage, "switch" can have 3 distinct behaviors when it's fed an unexpected value:
- simply ignore it and behave as if no value at all was fed (no "default" clause)
- use the unexpected value
- generate an error (something like:
| #default = {{error|bla bla bla}}IOW, a value outside the list is either expected or an error (first case is also an error: editors expect parameter values to have an effect).
templatedata should be able to indicate whether for this template and this parameter it's "kosher" to feed a value outside of "expected". again, this is useful for wizards and linting tools
