parameter allows array values but only scalar limits

[christianrauch]

Bug report

There is a discrepancy in the API design of the parameter values in ParameterValue and their bounds in (ParameterDescriptor).

While the parameter value allows scalar and array types:
https://github.com/ros2/rcl_interfaces/blob/1.2.0/rcl_interfaces/msg/ParameterValue.msg#L12-L38
the bounds in FloatingPointRange and IntegerRange are arrays with a single entry:
https://github.com/ros2/rcl_interfaces/blob/1.2.0/rcl_interfaces/msg/ParameterDescriptor.msg#L32-L36

What is the meaning of the scalar/single-element-array parameter ranges for array values? Having the bounds defined as arrays suggests that they are supposed to be used element-wise, which is not possible with the current message definition.

Expected behavior

Parameter limits in FloatingPointRange and IntegerRange should have the same dimension than the parameter value, such that every element in the value has its own min/max range.

Actual behavior

Parameter limits are scalar / single-element-array.