recorder doesn't record Date header

[nschloe]

Describe the bug

My code verifies server responses to prevent man-in-the-middle attacks. The signed data also includes the Date header, which is not present in the record. Hence, all verifications of recorded responses fail.

Fix: Add Date header to record.

Additional context

No response

Version of responses

0.25.7

Steps to Reproduce

See above.

Expected Result

See above.

Actual Result

See above.