Improve README for troubleshooting "project does not exist"

[eeaton]

TL;DR

Improve troubleshooting guidance in the readme for errors related to a project ID stored in terraform state when the GCP project doesn't exist. This is particularly common when a previous run failed due to project quota issues.

Example of somebody getting stuck, and detailed description of the fix, at: https://github.com/terraform-google-modules/terraform-example-foundation/issues/1187 https://github.com/terraform-google-modules/terraform-example-foundation/issues/488#issuecomment-973234938

Terraform Resources

n/a

Detailed design

n/a

Additional information

See also https://github.com/terraform-google-modules/terraform-example-foundation/issues/451

Common scenarios where the build can fail during tf apply after passing terraform validate

• quota issues
• values for project labels contain illegal character (could also improve this by setting conditional validation at the tf variable to catch it sooner)
• terraform apply fails due to a timeout

[eeaton]

As I'm cleaning up the backlog of issues, I've found a few issues around this same idea. I'll close a few as duplicates and keep the single issue open to track work.

• https://github.com/terraform-google-modules/terraform-example-foundation/issues/451
• https://github.com/terraform-google-modules/terraform-example-foundation/issues/488

• 1190

• 1257 ( not specifically about the project does not exist error, but similar as an edge case that happens when terraform fails midway through the apply state)