[cloud-app-engine-springboot]: extraction of standard project fails

[andreacipriani]

As per codelab, running

curl https://start.spring.io/starter.tgz \
  -d bootVersion=3.0.5 \
  -d dependencies=web \
  -d type=gradle-project \
  -d baseDir=gae-standard-example | tar -xzvf -

but it results into:

gzip: stdin: not in gzip format
tar: Child returned status 1
tar: Error is not recoverable: exiting now

[andreacipriani]

I think the issue is that bootVersion is too old, ideally it should be dynamically fetched as the latest version.