Fix structure for MongoDB Documents #4307

Description

Currently if you're using LuckPerms with MongoDB, the documents are formatted like this:

{
  _id: 'owner',
  permissions: [
    {
      key: 'PERMISSION',
      value: true
    },
    {
      key: 'PERMISSION',
      value: true
    }
  ]
}

Which is fine, but it's honestly less readable.

Proposed Behaviour

So instead this is a good idea:

{
  _id: 'owner',
  permissions: {
    "PERMISSION": true
  }
}

Which is not only (i think so) is smaller, but more readable. For the indexes, I honestly don't know what to do for that one.

Extra Details

No response