In order to remove the deprecated flag_undefined_default=True
argument, this commit updates the following flags to always be
enabled using a new temporary class:

- course_experience.course_outline_page
- course_experience.unified_course_tab

Adds a temporary setting `USE_DEFAULT_TRUE_NAMESPACE`,
to enable a monitored rollout of this change.

TNL-7061 is the ticket where these flags will actually be
removed. This requires more careful work including removing
all dead code, and potentially refactoring tests that were
testing shared functionality, but only when the flag was
False.

ARCHBOM-1316

When checking if consent is needed, ignore any enterprise
learner details that are not for the learner's currently
active enterprise.

ENT-3049

- Looks at masquerading config for dates, outline, metadata, and
  celebration APIs in course_home_api / courseware_api.
- Consolidates and cleans up places we check whether masquerading
  gives us full access to a course.

ENT-2998

- set up util function to use Amazon SES for sending calendar
  sync emails.
- remove old sailthru code which we originally implemented for
  this functionality
- include ADR on our decision to use SES instead of Sailthru.

[BD-10] [DEPR-83]

- add serializer mixin to expose date banner info
- add endpoint to reset deadlines for a sepcific course

Simplify how the course-outline template context is constructed to bring it into parity with other template contexts

Only actually reset user schedule if they have missed deadlines and not missed any gated content deadlines

Fixing RemovedInDjango30Warnings

**Background:** The `django.shortcuts` method `render_to_response` became deprecated in [Django 1.3](https://docs.djangoproject.com/en/3.0/releases/1.3/), when  `render` was introduced.

Per the documentation:

> render() is the same as a call to render_to_response() with a context_instance argument that forces the use of a RequestContext.

Both return an `HttpResponse` object.

**Context:** We changed two statements: An import line and the call to the method, adding explicit parameter names to improve readability.

**Before:**
```
from django.shortcuts import get_object_or_404, render_to_response
...
return render_to_response("teams/teams.html", context)


```

**After**
```
from django.shortcuts import get_object_or_404, render
...
return render(
            request=request,
            template_name="teams/teams.html",
            context=context
        )

```

Appending the assignment type to each graded
assignment on the Dates Tab. Exposed the 'format'
field, which corresponds to the graded assignment type.

Reducing dates widget to one assignment. Adding link to dates
page in the dates widget

Only mark a section as containing gated content if the content is *only* available to full-access learners

Refactor dates_banner_should_display to only return a single value, and to have a clearer set of conditions

This reverts commit c3ec8b83, reversing
changes made to 4252b149.

Only prompt to upgrade in order to completed graded content (or shift dates) when content_type_gating is enabled

This takes over some of the logic in the is_enabled property which
previously checked two things: (1) is the date time-sensitive and
(2) is the date even applicable to this course.

Now, is_enabled is only responsible for time-sensitive checks and
the new is_allowed property checks applicability.

In this way, we can more cleanly separate whether a date block
should show up on the dates sidebar (is_enabled and is_allowed)
and the dates tab (is_allowed).

REV-1153

Use a fixed time for course duration limits, so that schedule extensions don't extend FBE duration limits

REV-1153