implement proper child->parent relationships in queue implementations

[benluelo]

we don't currently handle this at all in either `pg-queuee:

union/lib/pg-queue/src/lib.rs

Line 101 in 86265eb

// TODO: Handle parent ids properly

union/lib/pg-queue/src/lib.rs

Line 254 in 86265eb

// TODO: Handle parent ids properly

for the in-memory queue the logic is written, but i have little to no faith in it's implementation as it is largely untested:

union/lib/queue-msg/src/lib.rs

Line 1018 in 86265eb

impl<T: QueueMessage> Queue<T> for InMemoryQueue<T> {

rather than duplicating this logic between both implementations, we should perhaps revisit the Queue<T> abstraction and see if we can come up with a better design.

it would also be helpful if we provided some sort of testing framework for plugin authors to test their implementations of run_pass to ensure that they're handling ids properly.