*feature request* PramFlowRule support multiple parameters, and nested fields

*feature request*

PramFlowRule support multiple parameters.
and support selecting some nested fields in objects. e.g. select only `uid`
```
{
"uid": 1234,
"payload": {...}
}
```

Start by locating PramFlowRule and its existing parameter-handling entry points; the issue names no files or tests. Determine how multiple parameters and selecting nested object fields should be represented, then add coverage showing both requested behaviors and verify existing rule handling remains intact.

Written by the indexing model from the issue text.