## 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
* [forwardport] fix(webconnectivity): send specific user agent (#615)
This forward ports b8c530388e66b2cc86abad26d077202782e4a823 to `master`.
See https://github.com/ooni/probe/issues/1902
* fix(websteps): send the correct user agent
Also related to https://github.com/ooni/probe/issues/1902: let's just
ensure that also websteps behaves in the correct way.
This change should simplify the pipeline's job.
Reference issue: https://github.com/ooni/probe/issues/1817.
I previously dismissed this possibility, but now it seems clear it
is simpler to have a very tabular data format internally and to
convert such a format to OONI's data format when serializing.
The OONI data format is what the pipeline expects, but processing
is easier with a more linear/tabular format.
This diff adds the prototype websteps implementation that used
to live at https://github.com/ooni/probe-cli/pull/506.
The code is reasonably good already and it's pointing to a roaming
test helper that I've properly configured.
You can run websteps with:
```
./miniooni -n websteps
```
This will go over the test list for your country.
At this stage the mechanics of the experiment is set, but we
still need to have a conversation on the following topics:
1. whether we're okay with reusing the data format used by other
OONI experiments, or we would like to use a more compact data
format (which may either be a more compact JSON or we can choose
to always submit compressed measurements for websteps);
2. the extent to which we would like to keep the measurement as
a collection of "the experiment saw this" and "the test helper
saw that" and let the pipeline choose an overall score: this is
clearly an option, but there is also the opposite option to
build a summary of the measurement on the probe.
Compared to the previous prototype of websteps, the main
architectural change we have here is that we are following
the point of view of the probe and the test helper is
much more dumb. Basically, the probe will choose which
redirection to follow and ask the test helper every time
it discovers a new URL to measure it w/o redirections.
Reference issue: https://github.com/ooni/probe/issues/1733
