Add backup-version file in backup tarball

[wwitzel3]

Closes #134

[wwitzel3]

@ncdc PTAL

[skriss]

Now that I'm thinking about this PR - we will now store some metadata as objects directly in object storage (e.g. ark-backup.json), and some (e.g. backup-version) as files within the tarball. Do we have a principled stance on what should go where? Would it make sense to duplicate any of it?

[nrb]

@skriss That's a good question on the duplication. My current thought is that the backup version should be in the tarball, so that it could be processed if moved around. Information that's useful for periodic checks should be outside the tarball, though, since we don't want to download and extract them all on a regular basis.

[wwitzel3]

I remember during the original discussion we wanted to intentionally keep backup-version in the tarball for the reason mentioned by @nrb

[wwitzel3]

So where did we land on this? There was also some conversation in #ark-dr that I wanted to echo here.

I am going to update this so that we will have a metadata folder which will hold the backup-version file in the backup tarball.

[ncdc]

Nolan is correct - we want the backup-version somewhere in the tarball so that we can identify its format version even if we don't have the json to go with it. Maybe we should also include the json in it as well...

👍 to metadata/backup-version or even just metadata/version

[skriss]

SGTM for now, though we probably need more thinking/work about how a tarball without an ark-backup.json file would be portable, if that's a goal. Can address later.

[ncdc]

I guess it probably can't be 100% portable, since we have other information in the bucket (snapshot details, logs)

[skriss]

this lgtm pending moving the file into a metadata/ dir

[wwitzel3]

Ok, I think this is ready to go now. PTAL @skriss @ncdc

[skriss]

lgtm

[wwitzel3]

This is ready to merge if everyone is happy with it.

[nrb]

Changes LGTM.

[carlisia]

I like this trend of moving logic and data to outside of controllers. This lgtm. 👍

[skriss]

@ncdc I think we were just waiting for your approval here since you had a comment - merge if happy :)

[ncdc]

Didn't realize y'all were waiting on me!