support user info variables as lists to be used in permissions

[ecthiender]

Right now the user info variables (as headers, from JWT claims or from webhook response) are converted into map of strings to strings. Support should be added for lists as well. Then in the permission system _in can be used with session variables.

See #1314

[lanex-victor]

Definitely looking forward for this to be added. Hope sooner..

[pilattebe]

For string columns you can send "X-Hasura-Variable":(${IdArray.join("|")})
Then restrict

{
    id: _similar: "X-Hasura-Variable"
}

It is a REGEX-like. id1 will match (id1|id2|id3) but not id4
Only works for strings tho.

[0x777]

added in f1cf6d0. See #2475