feat: add data attributes definition for learning subdomain

[mariajgrimaldi]

Description:
This PR adds class definitions for the objects that will be sent by Open edX events, they are based in the library

JIRA:
https://edunext.atlassian.net/browse/PS2021-629?atlOrigin=eyJpIjoiODIwNDA5M2MxZGRlNGQ2NjhjNjJhZWIwNWZiNWNlYjUiLCJwIjoiaiJ9

Dependencies:
This PR depends on #7

Testing instructions:
In your Open edX devstack

1. Go to lms shell make lms-shell
2. Install openedx-events specifying the events definition branch:
   pip install git+https://github.com/eduNEXT/openedx-events.git@MJG/event_data#egg=event_data
3. Go to the lms Django shell: python manage.py lms shell
4. Now, you can import the platform objects and map them to attrs classes. For example, you could do:

>>> from common.djangoapps.student.models import CourseEnrollment
>>> from openedx_events.learning.data import CourseEnrollmentData, UserData, UserPersonalData, UserNonPersonalData, CourseOverviewData
>>> course_enrollment = CourseEnrollment.objects.get(id=1)

*** MAPPING CourseEnrollment to CourseEnrollmentData ***
>>> course_enrollment_data = CourseEnrollmentData(
...                             user=UserData(
...                                 user_pii=(
...                                       username=course_enrollment.user.username,
...                                       email=course_enrollment.user.email,
...                                       name=course_enrollment.user.profile.name                                 
...                                  ),
...                                 user_non_pii=(
...                                       id=course_enrollment,ent.user.id,
...                                       is_active=course_enrollment.user.is_active
...                                 ),
...                             ),
...                             course=CourseOverviewData(
...                                 course_key=course_enrollment.course.id,
...                                 display_name=course_enrollment.course.display_name
...                             ),
...                             mode=course_enrollment.mode,
...                             creation_date=course_enrollment.created,
...                             is_active=course_enrollment.is_active
...                         )
>>> print(course_enrollment_data)
>>> import attr
>>> attr.asdict(course_enrollment_data)

Reviewers:

• tag reviewer
• tag reviewer

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)

Author concerns: List any concerns about this PR - inelegant
solutions, hacks, quick-and-dirty implementations, concerns about
migrations, etc.

[mariajgrimaldi]

Hey @ormsbee! We followed your suggestions. Now, the user is divided into two parts with PII and non-PII information

[mariajgrimaldi]

Hey again @ormsbee! We added the previous status for the certificate!

We'll make a mental note to review this again when using this data class in the platform! Thank you for the suggestion

[mariajgrimaldi]

Hey @feanil!
We also changed StudentData to UserData :)

[felipemontoya]

I see you put it in the UserNonPersonalData attr class. Given the "LMS user_id can be used for public events" portion of OEP-32 I think we are in the clear

[felipemontoya]

I'd like to keep the access to the user data a little less convoluted.
With this, to access the ID, one would need to call user_data_obj.user_non_pii.id

We could do something like:

@attr.s(frozen=True)
class UserNonPiiData:
    id = attr.ib(type=int)
    is_active = attr.ib(type=bool)


@attr.s(frozen=True)
class UserPiiData:
    username = attr.ib(type=str)
    email = attr.ib(type=str)
    name = attr.ib(type=str, factory=str)


@attr.s(frozen=True)
class UserData(UserNonPersonalData):
    pii = attr.ib(type=UserPersonalData)


user_data_obj = UserData(
    pii=UserPiiData(
        username="course_enrollment.user.username",
        email="course_enrollment.user.email",
        name="course_enrollment.user.profile.name"
    ),
    id=1,
    is_active=True
)

So the access is more direct, but we still make a strong distinction for pii data.

[felipemontoya]

I had to remove the is_active default when testing on the interactive console