Add HTTP Expires header in CRL download

[rohan-wire]

Name of feature:

HTTP Expires header in CRL download

Pain or issue this feature alleviates:

Allows caching of CRLs to be coordinated with actual CRL expiration date/time.

Why is this important to the project (if not answered above):

Is there documentation on how to use this feature? If so, where?

Happens automatically with no configuration required.

In what environments or workflows is this feature supported?

Whenever CRLs are enabled

In what environments or workflows is this feature explicitly NOT supported (if any)?

When CRLs are not enabled

Supporting links/other PRs/issues:

💔Thank you!

[CLAassistant]

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1 out of 2 committers have signed the CLA.

:white_check_mark: beltram
:x: rohan-wire
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