Display changes to stage/env-var changes during Deploy

[henders]

At the moment we display all the git commits that occurred since the last deployed version. It would be great to also display any changes to the stage configuration including commands/environment-variables/secrets so that a deployer can know there are potentially other things that changed besides code that could break the deploy.

[henders]

This happened to us where we deployed a new version but a change to a project environment variable by someone else actually broke it and we wasted a significant amount of time ruling out any code changes that might have affected it.

[grosser]

that should be possible with:

• a general "Stage changes" feature that looks at the audits generated since the last deploy
• kubernetes: diffing the release doc with the previous deploy (will show secrets path changes ... could maybe also add hashed values)

we currently do some basic "did the stage change since last deploy" logic, but it's not very reliable ...

/cc @ragurney @jonmoter