Feat: enrollments can expire

[angela-tran]

Closes #2062

This PR reverts "Revert "Feat: enrollments can expire (#1989)" (#2052)".

There were merge conflicts with various features and refactors that were done since #2052, and I think I resolved them all correctly. (Examples are system enrollment error logic and enrollment success template refactor.)

[github-actions]

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File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
benefits
settings.py
benefits/enrollment
views.py
Project Total

This report was generated by python-coverage-comment-action

[angela-tran]

I manually tested the expiration scenarios in enrollment:index using the MST Courtesy Card group in QA. With the fix from cal-itp/littlepay#64, they work for me.

benefits/benefits/enrollment/views.py

Lines 117 to 155 in 2a80a60

	if eligibility.supports_expiration:
	# set expiry on session
	if already_enrolled and group_funding_source.expiry_date is not None:
	session.update(request, enrollment_expiry=group_funding_source.expiry_date)
	else:
	session.update(request, enrollment_expiry=_calculate_expiry(eligibility.expiration_days))
	if not already_enrolled:
	# enroll user with an expiration date, return success
	client.link_concession_group_funding_source(
	group_id=group_id, funding_source_id=funding_source.id, expiry=session.enrollment_expiry(request)
	)
	return success(request)
	else: # already_enrolled
	if group_funding_source.expiry_date is None:
	# update expiration of existing enrollment, return success
	client.update_concession_group_funding_source_expiry(
	group_id=group_id,
	funding_source_id=funding_source.id,
	expiry=session.enrollment_expiry(request),
	)
	return success(request)
	else:
	is_expired = _is_expired(group_funding_source.expiry_date)
	is_within_reenrollment_window = _is_within_reenrollment_window(
	group_funding_source.expiry_date, session.enrollment_reenrollment(request)
	)
	if is_expired or is_within_reenrollment_window:
	# update expiration of existing enrollment, return success
	client.update_concession_group_funding_source_expiry(
	group_id=group_id,
	funding_source_id=funding_source.id,
	expiry=session.enrollment_expiry(request),
	)
	return success(request)
	else:
	# re-enrollment error, return enrollment error with expiration and reenrollment_date
	return reenrollment_error(request)

[angela-tran]

Rebased on top of latest dev

[lalver1]

I was able to test the different expiration scenarios for enrollments and they worked. Looking over the code, everything looked good too 👍