Workflow fails if PHP Version is undefined

[GlitchWitch]

As of #44 it seems that the workflow now always includes the PHP version in the POST request regardless of it is set.

This causes site creation to fail if a PHP version is not defined in the workflow file, despite the variable not being required.

(This issue was originally flagged by @noahc3)

[GlitchWitch]

WIP PR in #48

[GlitchWitch]

It looks like manually setting the php version results in the following error;

"Resource not found."
Error: Forge API request failed with status code 404.

[bakerkretzmar]

Should be fixed in v2.7.1, thanks! Forge must have turned off the empty strings to null middleware or something because I think we've always been sending this empty string.

[GlitchWitch]

Thanks @bakerkretzmar, I believe we are still running into the secondary issue I mentioned. Myself, @noahc3, and @DanielCoulbourne were unable to determine the cause of the 404 issue that presented when using branch from #48 or setting the PHP version manually.

[bakerkretzmar]

Hmm. Were you including the PHP version in the format php##, like php83? And it's a PHP version that is already installed on the server?

[noahc3]

Posted details in #50 to keep things organized :)