feat: handle 'session not found' errors

[oprudkyi]

fixes #37

There are a few cases when a 'Session not found' error can
happen:

• Scripts that idle too long - for example, a Laravel queue worker
  or anything that doesn't call Spanner frequently enough (more than once an hour).
• The session is more than 28 days old.
• Some random flukes on Google's side.

[taka-oyama]

Hi thanks for the pull request! I have some review feedback. Please check it out.

[taka-oyama]

Thank you for your contribution!

[taka-oyama]

I will release the next version once I fix the Phpstan errors.

[oprudkyi]

Hi @taka-oyama

Thank you.
could you also please create branch v3 from https://github.com/colopl/laravel-spanner/tree/v3.9.3
so it will be possible to backport to older laravel ?

[taka-oyama]

Hi, thanks for the patience.

Yes, I will backport it.

I couldn't find time this week so I will do it on monday.

[oprudkyi]

HI @taka-oyama
I thought to make a backport by self - the my whole endeavor was to get universal solution for Laravel 8.
But any solution will do.

[taka-oyama]

Hi. I released v4.1.0 and 3.10.0 (for laravel 8 or below), please check it out.

[taka-oyama]

Asking google to fix this upstream, so we don't have to do this hack.