[Extensibility Request][E-Document] Enable extension of Import Process 2.0

Describe the issue

We are trying to implement document import process from our OCR using E-Document.

We are starting with a basic customization - to control over Text to Account mapping, that was done previously via premapping codeunits in Data Exchange.

Import Version 1.0 logic ignores our premapping changes, and we do not have control over what items and accounts will be used for purchase lines.

So we are trying to implement Import Version 2.0 which is stated as current in E-Document docs. We are following this manual: https://github.com/microsoft/BCApps/blob/main/src/Apps/W1/EDocument/App/docs/extensibility.md.

But every object we need to is internal (e.g. E-Document Purchase Line/Header which are parameters to the interfaces that need to be implemented according to the docs).

That is why we are lost in how to use E-Document feature at all. Is it now exclusively created for Payables Agent alone?

Expected behavior

Be able to extend E-Document functionality according to documentation.

Steps to reproduce

1. Create an extensibility app.
2. Try to implement IPurchaseLineProvider interface.

Additional context

No response

Start with src/Apps/W1/EDocument/App/docs/extensibility.md and the IPurchaseLineProvider interface described there. Reproduce the issue by creating an extensibility app and attempting to implement that interface, then inspect which E-Document Purchase Line/Header objects are inaccessible. Done means the documented Import Process 2.0 extension path can be used by an external app.