Consider adding Hypothesis for property-based testing of authorization logic

[adamtheturtle]

Summary

The authorization_header() and related functions build HMAC-SHA1 signatures from (method, content, content_type, date, request_path). This is ideal for property-based testing.

Benefits

• Determinism: Same inputs should always produce the same output — trivial to verify with @given(st.text(), st.binary(), ...)
• Robustness: Edge cases — empty content, Unicode, very long strings, special characters in method/path — would be systematically explored
• No crashes: authorization_header should never raise on valid-type inputs

Suggested properties

1. authorization_header(access_key=k, secret_key=s, method=m, content=c, ...) is deterministic for fixed inputs
2. Empty content (None, b"", "") is handled correctly
3. Unicode in content is encoded without crashing
4. Arbitrary request_path strings (including special chars) produce valid output

Note

.hypothesis/ is already in .gitignore, suggesting Hypothesis may have been considered. No implementation exists yet.