feat: add 1st batch of filters

[mariajgrimaldi]

Description:

This PR adds:

• PreRegisterFilter: intended to be executed before the registration process starts.
• PreLoginFilter: intended to be executed before the login process starts.

Used by edx-platform.

Testing instructions:

1. Install openedx-filters using this branch.
2. Use this edx-platform branch MJG/1st_filters_batch
3. In your favorite plugin, create some filter steps. For example:

class ModifyUsernameBeforeRegistration(PipelineStep):

    def run_filter(self, form_data):
        username = f"{form_data.get('username')}-edunext"
        form_data["username"] = username
        return {
            "form_data": form_data,
        }

These sample filter steps are implemented in this plugin

4. Add the following Django settings to your configuration file:

OPEN_EDX_FILTERS_CONFIG = {
    "org.openedx.learning.course.enrollment.started.v1": {
        "fail_silently": False,
        "pipeline": [
            "openedx_filters_samples.samples.pipeline.ModifyModeBeforeEnrollment",
            "openedx_filters_samples.samples.pipeline.StopEnrollment"
        ]
    },
    "org.openedx.learning.student.login.requested.v1": {
        "fail_silently": False,
        "pipeline": [
            "openedx_filters_samples.samples.pipeline.ModifyUserProfileBeforeLogin",
            "openedx_filters_samples.samples.pipeline.StopLogin"
        ]
    },
    "org.openedx.learning.student.registration.requested.v1": {
        "fail_silently": False,
        "pipeline": [
            "openedx_filters_samples.samples.pipeline.ModifyUsernameBeforeRegistration",
            "openedx_filters_samples.samples.pipeline.StopRegister"
        ]
    }
}

With this configuration, you won't be able to register, login, or enroll in a course. Another configuration you could try is, instead of Stop<process> use NoopFilter

Reviewers:

• @felipemontoya

Merge checklist:

• All reviewers approved
• CI build is green
• Version bumped
• Changelog record added
• Documentation updated (not only docstrings)
• Commits are squashed

Post merge:

• Create a tag
• Check new version is pushed to PyPI after tag-triggered build is
  finished.
• Delete working branch (if not needed anymore)

[mariajgrimaldi]

should we move all filters to learning/filters.py file? @felipemontoya to be compliant with openedx-events

[felipemontoya]

We have indeed most signal definitions for events at learning/signals.py, which suggests that we should also move to learning/filters.py.

If we don't, then we will have a filter:
"org.openedx.learning.student.registration.requested.v1"
defined at openedx_filters.learning.auth.PreRegisterFilter.

If we do, then we are looking at:
"org.openedx.learning.student.registration.requested.v1"
defined at openedx_filters.learning.filters.PreRegisterFilter.

which is a little more consistent with from openedx_events.learning.signals import SESSION_LOGIN_COMPLETED which is a live example from the events implementation.

[felipemontoya]

We have indeed most signal definitions for events at learning/signals.py, which suggests that we should also move to learning/filters.py.

If we don't, then we will have a filter:
"org.openedx.learning.student.registration.requested.v1"
defined at openedx_filters.learning.auth.PreRegisterFilter.

If we do, then we are looking at:
"org.openedx.learning.student.registration.requested.v1"
defined at openedx_filters.learning.filters.PreRegisterFilter.

which is a little more consistent with from openedx_events.learning.signals import SESSION_LOGIN_COMPLETED which is a live example from the events implementation.

[felipemontoya]

Although I find the names "PreRegisterFilter" or "PreLoginFilter" very easy to understand, I think that we set an important precedent at the events library. There we have:

COURSE_ENROLLMENT_CREATED:
    event_type="org.openedx.learning.course.enrollment.created.v1"

STUDENT_REGISTRATION_COMPLETED:
    event_type="org.openedx.learning.student.registration.completed.v1"

COURSE_UNENROLLMENT_COMPLETED
    event_type="org.openedx.learning.course.unenrollment.completed.v1"

While in this PR we are proposing:

PreRegisterFilter:
    filter_type = "org.openedx.learning.student.registration.requested.v1"

We could change this so that the name matches a little better the filter_type.
For example we could use any of the following as the class names:

• StudentRegistrationRequested
• StudentRegistrationStarted
• StudentRegistrationFilter

[felipemontoya]

This probably also affects the naming of the PreEnrollmentFilter and the implementing PR as well

[mariajgrimaldi]

Great suggestion. I'll go with the StudentRegistrationRequested because it's the closest to the events naming convention.

[felipemontoya]

Is password enough? should we be censoring all the fields at https://github.com/edx/edx-platform/blob/master/common/djangoapps/track/middleware.py#L64

[felipemontoya]

This is looking almost ready to me now. I left a comment about the name of the exception but once that is in, I''m good with merging.