[IDEA] Use of a JSON template file of the Power Platform environment in the provisioning pipeline about power-platform-alm-starter-kit

[BenediktBergmann]

I think a variable group could be good here. Might be an idea to use the approach we fell most comfortable with to get a first working version and possibly change it to the preferred method later.

[rpothin]

For the moment, I will try to use a variable group (library) to share variables across different pipelines.
Note to myself: need to update the README.md file regarding this new way to work with common variable.

[rpothin]

I will make some updates in the current PR to use a variable groups.

It will have some impacts in the pipelines and in the README.md file.