Configuration for parameter validation.
This message has
oneof_ fields (mutually exclusive fields).
For each oneof, at most one member field can be set at the same time.
Setting any member of the oneof automatically clears all other
Validation based on regular expressions. This field is a member of `oneof`_ ``validation_type``.
Validation based on a list of allowed values. This field is a member of `oneof`_ ``validation_type``.