Allowing session cookie (split cookie)

[JeremyPasco]

AS described in #809, the split cookie approach cannot be fully implemented because this bundle doesn't allow session cookie (when lifetime=0, then the token ttl value was used instead). This pull request allows a 0 lifetime cookie:

lexik_jwt_authentication.yaml

lexik_jwt_authentication:
    secret_key: '%env(resolve:JWT_SECRET_KEY)%'
    public_key: '%env(resolve:JWT_PUBLIC_KEY)%'
    pass_phrase: '%env(JWT_PASSPHRASE)%'
    token_ttl: 86400
    token_extractors:
        split_cookie:
            enabled: true
            cookies:
                - jwt_hp
                - jwt_s
    set_cookies:
        jwt_hp:
            lifetime: 360
            samesite: strict
            path: /
            domain: null
            httpOnly: false
            split:
                - header
                - payload

        jwt_s:
            lifetime: 0 # session cookie here
            samesite: strict
            path: /
            domain: null
            httpOnly: true
            split:
                - signature

[chalasr]

Thanks a lot for the PR! Could you please add a test case?

[JeremyPasco]

Done :)
I also updated the documentation for split_cookie to reflect the idea behind this article: the signature cookie should be a session one.

[chalasr]

Sorry for not reviewing this earlier, my open-source time was quite limited these 2 last weeks.
I'm going to have a deep look at this as soon as possible.

[chalasr]

I kinda messed up with git while merging, but everything is ok. Thank you very much @JeremyPasco.