T14688 session key unique

[niden]

Hello!

• Type: bug fix
• Link to issue: [BUG]: Can't read session vars provided by another app  #14688

In raising this pull request, I confirm the following:

• I have read and understood the Contributing Guidelines
• I have checked that another pull request for this purpose does not exist
• I wrote some tests for this PR
• I have updated the relevant CHANGELOG
• I have created a PR for the documentation about this change

Fixed Phalcon\Session\Manager::getUniqueKey to prefix the key only if uniqueId is present

Thanks

[ruudboon]

Thnx. Looks good to me.

[codecov]

Codecov Report

Merging #14689 into 4.0.x will increase coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##            4.0.x   #14689      +/-   ##
==========================================
+ Coverage   67.92%   67.92%   +<.01%     
==========================================
  Files         483      483              
  Lines      111477   111483       +6     
==========================================
+ Hits        75724    75730       +6     
  Misses      35753    35753