Before finishing the ongoing refactoring and leaving whatever
is left of netx in tree, I would like to restructure it so that
we'll have an easy time next time we need to modify it.
Currently, every functionality lives into the `netx.go` file and
we have a support file called `httptransport.go`.
I would like to reorganize by topic, instead. This would allow
future me to more easily perform topic-specific changes.
While there, improve `netx`'s documentation and duplicate some of
this documentation inside `internal/README.md` to provide pointers
to previous documentation, historical context, and some help to
understand the logic architecture of network extensions (aka `netx`).
Part of https://github.com/ooni/probe-cli/pull/396
## Checklist
- [x] I have read the [contribution guidelines](https://github.com/ooni/probe-cli/blob/master/CONTRIBUTING.md)
- [x] reference issue for this pull request: https://github.com/ooni/probe/issues/1885
- [x] related ooni/spec pull request: N/A
Location of the issue tracker: https://github.com/ooni/probe
## Description
This PR contains a set of changes to move important interfaces and data types into the `./internal/model` package.
The criteria for including an interface or data type in here is roughly that the type should be important and used by several packages. We are especially interested to move more interfaces here to increase modularity.
An additional side effect is that, by reading this package, one should be able to understand more quickly how different parts of the codebase interact with each other.
This is what I want to move in `internal/model`:
- [x] most important interfaces from `internal/netxlite`
- [x] everything that was previously part of `internal/engine/model`
- [x] mocks from `internal/netxlite/mocks` should also be moved in here as a subpackage
* doc: ensure all top dirs have an explanatory README
This makes the repository a lil bit nicer to newcomers.
Part of https://github.com/ooni/probe/issues/1335
* fix: re-run bindata to embed the README
The readme is small, so we can pay the price of adding it.
On a related note, I am very pleased the Go team implemented the
`//go:embed` feature, so we can get rid of this bindata thing.
