shards prune for tenant_id=current_user

I'm testing Citus to scale a multi-tenant application that has about 1000 tenants.
Actually I'm using a single node postgresql, using RLS + partitions by tenant.

The problem that I found in Citus is that shards prune doesn't work for: "where tenant_id=current_user", it only work if you compare to a literal: "where tenant_id='tenant00001'".

Currently RLS policies for each table are:

```
CREATE POLICY tenant_isolation_policy
ON public.table_a
AS PERMISSIVE
FOR ALL
TO public
USING ((tenant_id = current_user));
```

If I do explain analyze for a simple select, I found that shards pruning is not working:
```
" Task Count: 32"
" Tuple data received from nodes: 14 kB"
" Tasks Shown: One of 32"
```

But if I write the policy as:
```
CREATE POLICY tenant_isolation_policy
ON public.table_a
AS PERMISSIVE
FOR ALL
TO public
USING ((tenant_id = 'tenant00001'));
```

It do shard pruning:
```
" Task Count: 1"
" Tuple data received from nodes: 14 kB"
" Tasks Shown: All"
```

As a reference, using RLS + partitions by tenant, partition prune works all the time.

I have no way to rewrite application to add tenant_id as a literal in each query, is there any other solution?
Could this be improved in a future version?