Feature Request: Add support for symmetric bundles

[thoughtrealm]

Currently, all bundles use a hybrid pattern with an asymmetrically encrypted header and a symmetrically encrypted payload. The asymmetric functionality is supported by identities in the profile stores.

There is current support for symmetric only outputs relating to the exports and the private key store.

We want to support creating symmetric bundles. This is to support a backup feature and similar functionality, where we can bundle the entire profile path or some parts of it, while just using a user supplied symmetric key. The reason for this is that the profile backups will contain the actual profile identities, so you don't have those available when restoring the backup. For this reason and others, we will support a symmetric output feature.

Requirements:

• This will require a key to be provided during the bundle command and during the open command.

• A different header will be required than the asymmetric bundle's header.

• This functionality should be written in a way that it can be re-used easily for the upcoming backup and restore functionality.

The backup and restore functionality will take as input the path to the profile root or one of the profile paths. It will pass this to a symmetric output bundle process. The restore will do something similar, but in the other direction.

This new symmetric functionality should accomodate this.