feat: add CoursewareViewRedirectURL pipeline steps

[pwnage101]

This commit replaces most enterprise-specific logic serving the purpose
of conditionally blocking courseware access.

Enterprise steps added:

• EnterpriseStartDateAccessFailureStep supplies an enterprise-specific start-date error for enterprise learners.
• ActiveEnterpriseCheckStep denies access when the learner's active EnterpriseCustomer differs from the enrollment's customer.

Consent steps added:

• DataSharingConsentRedirectStep supplies a redirect URL to collect data sharing consent when it is required.
• DataSharingConsentCourseAccessStep denies access when consent is required.

ENT-11544

---

Blocked by:

• feat: add CoursewareViewStarted, CourseStartDateValidationFailed, and CoursewareAccessChecksRequested filters openedx-filters#336

Blocks:

• feat: decouple enterprise from courseware view redirects, course start-date validation, and course access checks openedx-platform#38102

[codecov]

Codecov Report

❌ Patch coverage is 62.06897% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.00%. Comparing base (306ca8a) to head (b4c83bf).

Files with missing lines	Patch %	Lines
consent/helpers.py	50.00%	11 Missing ⚠️

❌ Your patch check has failed because the patch coverage (62.06%) is below the target coverage (95.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2548      +/-   ##
==========================================
- Coverage   86.04%   86.00%   -0.04%     
==========================================
  Files         250      251       +1     
  Lines       16700    16740      +40     
  Branches     1657     1662       +5     
==========================================
+ Hits        14369    14397      +28     
- Misses       1997     2008      +11     
- Partials      334      335       +1     

Flag	Coverage Δ
unittests	86.00% <62.06%> (-0.04%)	⬇️

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