Inconsistent session variable format when using _in VS _contained_in operators

### Version Information

Server Version:
CLI Version (for CLI related issue):

### Environment

### What is the current behaviour?

In our application, we have a session variable set as a JSON array like so:

Which we then use in some of our tables to set permissions using the `_contained_in` operator, like so:

The `value` column also being of JSON type, this works great.

However, we recently introduced another table, which contains a simple text column on which we tried to set similar permissions using `_in` operator. Queries against this table always return no result:

Upon taking a closer look at the documentation, it seems the `_in` operator expects a session variable using a slightly different format: `{123456, 789012, ... }` (essentially using `{}` instead of `[]`).

I tried switching to this format, which works for the second table, but fails when querying the first table with `malformed array literal`, making it seemingly impossible to mix and match these operators across our schema...

### What is the expected behaviour?

Ideally, both `_in` and `_contained_in` should accept the same session variable format.

### How to reproduce the issue?

1. Set a session variable as a JSON array
2. Set a table permission using `{"value":{"_contained_in":"x-hasura-user-groups"}}`
3. Set another table permission using `{"value":{"_in":"x-hasura-user-groups"}}`

### Screenshots or Screencast

### Please provide any traces or logs that could help here.

### Any possible solutions/workarounds you're aware of?

The only way I could think of working around this issue was to create a view and convert the text column to a JSON array with a single field using `jsonb_build_array` so we could continue to use `_contained_in`. This is fine for small tables, but far from ideal for larger ones:

```
CREATE OR REPLACE VIEW public.my_table_view
AS SELECT
jsonb_build_array(group) AS group,
...
FROM my_table;
```

### Keywords

Start by reproducing the permission rules from the issue with the JSON-array session variable, using both `_contained_in` and `_in`. Trace how each operator parses and compares the session variable value; done means both operators accept the same documented format without breaking the existing JSON-column behavior.

Written by the indexing model from the issue text.