Drop deprecated interval decorator from public API

[Copilot]

This change removes the deprecated interval decorator ahead of the major release, completing the planned API cleanup. Consumers should schedule interval-based jobs via cron(...) with APScheduler IntervalTrigger instead.

• Public API

  • Removed interval from crontask.__all__.
  • Removed the interval(*, seconds) decorator implementation from crontask/__init__.py.

• Code cleanup

  • Removed now-unused imports tied to the deprecated path (warnings, IntervalTrigger in crontask/__init__.py).

• Tests

  • Removed interval import usage in tests/test_tasks.py.
  • Removed the legacy test_interval__seconds test that validated deprecated behavior.

from apscheduler.triggers.interval import IntervalTrigger
from django.utils import timezone
from crontask import cron

@cron(IntervalTrigger(seconds=30, timezone=timezone.get_default_timezone()))
@task
def my_task():
    ...

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.81%. Comparing base (64b2891) to head (2eabb18).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #58      +/-   ##
==========================================
- Coverage   98.85%   98.81%   -0.04%     
==========================================
  Files           6        6              
  Lines         174      169       -5     
==========================================
- Hits          172      167       -5     
  Misses          2        2              

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