Gracefully fail when freshness cannot be calculated

[parkerhancock]

This is a simple change to remove a Runtime Error when a freshness can't be calculated. If freshness can't be calculated, then the request should be sent, rather than error out.

[codecov]

Codecov Report

Merging #104 (2e38f49) into master (8c31fe9) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #104   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           27        27           
  Lines         1666      1675    +9     
=========================================
+ Hits          1666      1675    +9     

Files	Coverage Δ
hishel/_controller.py	100.00% <100.00%> (ø)
tests/test_controller.py	100.00% <100.00%> (ø)

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[karpetrosyan]

Thank you very much; that makes sense.

So RFC 9111 says:

Caches are encouraged to consider responses that have invalid freshness information (e.g., a max-age directive with non-integer content) to be stale

That means we should re-validate the response instead of raising a RuntimeError.

[karpetrosyan]

Can you please add a test and changelog for this PR?

Here is how to test it:

def test_freshness_lifetime_invalid_information():
    controller = Controller()
    response = Response(
        status=200,
    )
    original_request = Request("GET", "https://example.com")
    request = Request("GET", "https://example.com")
    conditional_request = controller.construct_response_from_cache(
        request=request, response=response, original_request=original_request
    )
    assert isinstance(conditional_request, Request)

[parkerhancock]

Requested changes made! I also confirmed that the new test added actually tests for this change (I wrote the test, reverted the change to _controller.py, confirmed failing, restored change to _controller.py, test now passes).

[karpetrosyan]

Great job! Thank you @parkerhancock