Removed SessionIdentifierAwareInterface

[alexmerlin]

Q	A
Documentation	yes
Bugfix	no
BC Break	yes
New Feature	no
RFC	no
QA	no

Description

As requested in #59 this commit:

• adds SessionIdentifierAwareInterface's getId() method to SessionInterface
• removes SessionIdentifierAwareInterface

Also, adds v2 documentation.

[gsteel]

Code changes look 👍 - Just the redirects need updating

[gsteel]

Sorry @alexmerlin - I've just been checking the implementations due to the removed test testGetIdReturnsEmptyStringIfNoIdentifierProvidedToConstructor, and the session id is expected to be ''|non-empty-string. This is used to signal to persistence implementations that the session needs to be regenerated - My fault. It might have been clearer for the id to be typed as null|non-empty-string but it's not worth changing this for all the implementations.

I should have checked this out properly before opening my mouth! So the addition of non-empty-string needs to be reverted.

For future reference, the @psalm- prefix is generally unnecessary. Most IDEs along with Psalm and PHPStan understand non-empty-string and most other annotations. Notable exceptions to this rule are @psalm-type and @psalm-import-type

[gsteel]

Thanks @alexmerlin 👍

[froschdesign]

@alexmerlin @gsteel
Please make sure that all changes in the history are visible. The changes to the documentation are not available here as a separate pull request/commit.