own env option for 'sess_save_path'

[mheiduk]

Description

Adding possibility to easily change the path for the option 'sess_save_path' via an env variable.

Related Issue

#935
https://community.invoiceplane.com/t/topic/10166

Motivation and Context

At the moment a change isn't possible unless changing it directly in the config.php file. Should be available as an env option too in my opinion.

Screenshots (if appropriate):

Pull Request Checklist

• My code follows the code formatting guidelines.
• I have an issue ID for this pull request.
• I selected the corresponding branch.
• I have rebased my changes on top of the corresponding branch.

Issue Type (Please check one or more)

• Bugfix
• Improvement of an existing Feature
• New Feature

[nielsdrost7]

Thank you very much for the PR. I'll merge it for sure.
I was just thinking about 2 things:
The value in ipconfig.php.example. What should we put there?
Should we put this line in ipconfig.php.example?

Could you rebase 1 more time?
I've made a change in the development branch yesterday.
The exact same file

[mheiduk]

Already should have been rebased, I can see your commit in my branch.

I can put the line in ipconfig.php.example, but other env vars are missing too. If you want, I can also add the missing env vars and then we could merge.

[nielsdrost7]

Already should have been rebased, I can see your commit in my branch

You're right,my apologies.

I've decided against adding those other variables in the ipconfig.php.example file.
It could give more unnecessary questions.

Great job!
I'm merging your PR