Add multipart examples

[dmonakhov]

Please add examples of how to format envelop to as multi parts with specific size.
Since envelop is based on UR which supports multiparts it is perfect format for paper backup use case.
Where large document encoded envelop and spitted in to multiple parts and printed to paper, each QR part on a single page.

[shannona]

Multipart UR guide is here:
https://github.com/BlockchainCommons/Research/blob/master/papers/bcr-2024-001-multipart-ur.md

If there's anything that's missing, let us know!

[dmitry-monakhov]

https://github.com/BlockchainCommons/Research/blob/master/papers/bcr-2024-001-multipart-ur.md
This is an implementation guide, but not what I meant, but I'm talking about bc-envelope-cli example which any non technical person can use.
Ideally just add an example how to format large document https://github.com/BlockchainCommons/bc-envelope-cli-rust/blob/master/docs/Attachments.md

bc-envelop-cli is an amazing Swiss knife tool which can easily used for things like https://github.com/za3k/qr-backup, original project use home made approach for data encoding, but bc-envelop is founded on well written standards.

Here is an example: create an attachment, and format it as sequence of UR's with maximum size of 256 chars(this option is not implemented yet), and later generate sequence of png files which container muli-parts QRs which later can be printed on paper.

VENDOR="tar/xz"
CONFORMS_TO="https://example.com/attachment"
cat  my_file.tar.xz | envelope attachment create $VENDOR --conforms-to $CONFORMS_TO  | \
envelope format --type ur --max-size 256 | \
qrencode -o my_qr_backup_page

ls .

my_qr_backup_page-01.png
my_qr_backup_page-02.png
my_qr_backup_page-03.png
my_qr_backup_page-04.png

[shannona]

Gotcha. Thanks for the clarification.