Feat: Progressive/tiered lockouts based on failure count

[rodrigobnogueira]

What does this PR do?

This PR introduces the ability to configure progressive (tiered) lockouts in django-axes. Instead of a single fixed cool-off time, the system now supports escalating lockout durations based on the number of failed attempts.

Changes

• Added LockoutTier dataclass and the AXES_LOCKOUT_TIERS setting to configure the tiers in axes.conf.
• Modified core helpers (get_cool_off, get_failure_limit, get_lockout_message, get_lockout_response) in axes.helpers to resolve and apply the appropriate tier based on a request's axes_failures_since_start count.
• Added system checks (W007, W008) in axes.checks to warn users if AXES_LOCKOUT_TIERS is misconfigured or used alongside AXES_COOLOFF_TIME.
• Wrote comprehensive unit tests and check tests for the tiered lockout logic.
• Added documentation for AXES_LOCKOUT_TIERS to docs/4_configuration.rst.

How it works

Users can configure AXES_LOCKOUT_TIERS as a list of LockoutTier instances. For example:

from datetime import timedelta
from axes.conf import LockoutTier

AXES_LOCKOUT_TIERS = [
    LockoutTier(failures=3,  cooloff=timedelta(minutes=15)),
    LockoutTier(failures=6,  cooloff=timedelta(hours=2)),
    LockoutTier(failures=10, cooloff=timedelta(days=1)),
]

When AXES_LOCKOUT_TIERS is defined, it overrides both AXES_FAILURE_LIMIT (which becomes the threshold of the lowest tier) and AXES_COOLOFF_TIME. Lockouts are subsequently applied dynamically according to the rules defined in the tiers.

All existing behavior remains completely unchanged if AXES_LOCKOUT_TIERS is not set.

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.90%. Comparing base (c3dcd1b) to head (546cf4d).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
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+ Coverage   91.56%   91.90%   +0.34%     
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  Files          37       37              
  Lines        1268     1322      +54     
  Branches      172      183      +11     
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+ Hits         1161     1215      +54     
  Misses         83       83              
  Partials       24       24              

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[aleksihakli]

Hey, looks good, thanks, but this is a handful to review and a brand-new feature at that. I'll try to set some time aside later on for checking this out.