Add S3 v1 interface and update S3 v0 interface

[theoctober19th]

This PR aims to introduce a newer version of s3 interface (v1), which is going to be implemented by the s3-integrator on 2/ track going further. The new s3-integrator charm is added with features of automatic bucket creation and verification, as per the spec DA171.

The major changes in the interface is that now the sensitive information like access-key and secret-key are to be passed by encapsulating them in a Juju secret -- while other things being similar. The interface now also adds for support for both provider and requirer writing the version of the S3 lib they're using -- to enable us to have more flexibility in the future should we have the necessity to have conditional logic based on some specific version of charm lib.

This PR also aims to update some old and obsolete information on the s3 v0 interface.

[deusebio]

Thank you @theoctober19th for adding this! I believe it is very beneficial.

I just have a couple of questions on whether some fields are really optional, but otherwise everything looks good!

[james-garner-canonical]

Chiming in with my review since @dimaqq requested it. I'd love to see more in the v1 readme about the migration strategy for deployments, as well as some documentation (or a pointer to library docs) explaining which library versions support which interface versions.

[james-garner-canonical]

Hi @theoctober19th @Batalex @deusebio, we're moving towards archiving this repo very soon, however interface specifications live on in the charmlibs repo.

I'm happy to merge this PR and migrate the interface definition to charmlibs, but it looks like there are a couple of open questions from @deusebio and @Batalex that should be addressed first.

I also posted some documentation feedback, most of which is minor and can be skipped, but it would be great to get some documentation of migration strategies and the library versions that support the different interface versions.

[theoctober19th]

Hi @james-garner-canonical, thank you for the information that this repo is soon to be archived. I'll do the needful to get this merged ASAP.

[theoctober19th]

Hi @james-garner-canonical, I've added the requested changes in the PR. Can you have a look again?

[james-garner-canonical]

This looks good to me, thank you for adding the extra documentation and the Pydantic schema! I'll leave the PR open for now to give @Batalex and @deusebio a chance to reply, but it's good to merge from my perspective.

[deusebio]

Looks good! Thanks @theoctober19th !