[batch] warns the user if client or server is using deprecated functionality

[iris-garden]

Closes #14485.

Tested that this works by deploying the branch to my dev namespace and pointing my dev config at it:

hailctl dev deploy -b iris-garden/hail:batch/deprecated-apis -s deploy_batch,add_developers
hailctl dev config set default_namespace irademac

And then running the following:

from hailtop.batch import ServiceBackend
batch_client = await ServiceBackend(billing_project='test', remote_tmpdir='gs://irademac/test/')._batch_client()
# one of the deprecated endpoints
await batch_client._get("/api/v1alpha/batches/402/jobs/1/log")

[patrick-schultz]

Thanks Iris, this looks great! Just one concern.

[patrick-schultz]

I think warning whenever there is a newer release is probably too noisy. For now lets just warn when they are specifically depending on deprecated functionality.

If we did do this, we'd also need to be sure we're only comparing the release version, not the commit hash. Otherwise, since we deploy batch on every commit, every user would be out of date as soon as any PR merges after a release.

[iris-garden]

Good point! I had honestly not realized we deploy Batch on every commit. If at some point down the line we come up with a policy for e.g. how many patch versions the difference between client and server can be, we can always reintroduce the version checking, but for now I agree it doesn't need to be there. Removed!

_

[ehigham]

How many routes are we likely to deprecate? While this solution is fine I'm not too fond of the repeated route names.
Would a modified routes decorator that automatically adds this deprecation message be too complicated/overly fancy:

@get(route, deprecated=True)
async def get_foo(request: Request) -> Response: 
   ...


def get(path, deprecated: bool): 
    return route(routes.get, path, deprecated)

def post(path, deprecated):
    return route(routes.post, path, deprecated)

...

def route(verb, path, deprecated):
    def wrapper(fn):
        @verb(path)
        async def handler(request, *args, **kwargs):
            response = await fn(request, args, kwards)
            if deprecated:
                response.headers['X-Hail-Deprecated'] = (
                    f'The endpoint "{path}" is deprecated. '
                    'Please upgrade your Hail version to the latest release.'
                )
           return response
        return handler
    return wapper

[patrick-schultz]

I think that's fine if Iris wants to do it, but I expect deprecated endpoints to be pretty rare.

[ehigham]

This is a much nicer solution than I proposed. Thank you!

[iris-garden]

Thanks! Sorry, meant to reply to your comment after the tests ran but forgot