Bug: Cookie with SameSite.DEFAULT_MODE sends an empty SameSite= attribute #8708

Expected Behaviour

Cookie(..., same_site=SameSite.DEFAULT_MODE) leaves the SameSite attribute out of the Set-Cookie header, so the browser applies its default (the same as Go's http.SameSiteDefaultMode, which these names follow).

Current Behaviour

Cookie.__str__ checks if self.same_site:, which is true for every enum member, and DEFAULT_MODE has the value "", so the header gets an attribute with no value: SameSite=. That is not a valid SameSite value.

Code snippet

from aws_lambda_powertools.shared.cookies import Cookie, SameSite

str(Cookie(name="session", value="abc", same_site=SameSite.DEFAULT_MODE))
# 'session=abc; Secure; SameSite='

Steps to Reproduce

1. Create a Cookie with same_site=SameSite.DEFAULT_MODE.
2. Return it in a Response(cookies=[...]) or call str() on it.
3. The Set-Cookie value ends with SameSite=.

Possible Solution

Only write the attribute when the enum value is not empty. I can open a PR.

Powertools for AWS Lambda (Python) version

latest (develop, 3.38.0)

AWS Lambda function runtime

3.12

Packaging format used

PyPi

Debugging logs

No response