We want to be able to post invoices into the KSeF API and get back
the UPO that proves that the invoice has been accepted by the system.

The first step is communicating with the API to get the interactive
session. To get the interactive session we need to have the context
in which we send the requests this context is the tax id of the company.
Next we need a valid token from ksef it can be generated from
ksef.mf.gov.pl/web for production or from ksef-test.mf.gov.pl/web for
test. The last thing is the public key provided from https://ksef.mf.gov.pl/ and
https://ksef-test.mf.gov.pl/.

To get the session token we first need to get the authorization challenge for
our context. Then we use the context, token and authorization challenge to
create a interactive session and get the session token used in other requests.

We want to be able to post invoices into the KSeF API and get back
the UPO that proves that the invoice has been accepted by the system.

Here we prepare the request that posts the invoice to KSeF backend.
We also prepare a request that checks the invoice status.

With those requests we can post the invoice and check if it finished
processing.

We want to be able to post invoices into the KSeF API and get back
the UPO that proves that the invoice has been accepted by the system.

The UPO files are generated after the interactive session is terminated.
To get the files we first need to terminate the session then after it
finishes generating the UPO files we can get them from the session status request.

Here we the session termination and status requests used in the process.

We want to be able to post invoices into the KSeF API and get back
the UPO that proves that the invoice has been accepted by the system.

Here we get the parameters from the CLI and use the requests we prepared
to post the invoice and save the UPO. The example command would look like

go run ./cmd/gobl.ksef send ./test/data/out/invoice-pl-pl.xml 1234567788 624A48824F01935DADE66C83D4874C0EF7AF0529CB5F0F412E6932F189D3864A ./api/keys/test.pem