Improve error logging

[rukai]

While trying to get shotover to connect to redis on my local machine I ran into a few issues that were impossible to investigate due to error logging.
So this PR fixes those cases to be properly logged.
The issues were:

• Specifying a redis instance as part of a cluster that is not configured to run as a cluster.
• Connecting to a redis instance that does not exist.
• Attempting to load a config file that does not exist.

The config/topology.yaml seems to be specified in a previous? format as it needed to be changed to run on my machine.

[XA21X]

The config/topology.yaml seems to be specified in a previous? format

Yeah, I've been told we used to use a proper Redis client instead of rolling our own.
I've opportunistically re-added support for these full URIs in #101.

I'm not sure if we should keep /config, as it's not really a working example, especially without documentation.
The basic_driver_tests spins up Dockerised clusters to supplement the example Shotover config (see /examples).

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I hit most of those cases for missing error handling when I started. :')
I've also fixed some of them in a similar way in my PR.

[XA21X]

PR looks good to me. Probably best to wait for @benbromhead to review and merge.

[rukai]

Hmmm, whats the benefit of readding support for those URL's, surely the less things we have to parse the better?

I'm all for removing /config.
In that case we should also change the defaults on --config-file and --topology-file, although i'm not sure what exactly they should be changed to.
Maybe just config.yaml and topology.yaml?

We should also rename all the config.yaml's in examples/ to topology.yaml because its super confusing how it is atm.

[XA21X]

whats the benefit of readding support for those URL's

That's a good point. It has negative value right now so I will remove it. It was done while I was still trying to figure out the scope e.g. possibility of per-server authentication (or TLS) options, and I also thought it would be nice to get the existing inputs working before I started on a new feature, even though it was already broken.

we should also change the defaults on --config-file and --topology-file

Question is, should we expect the project root to be a somewhat usable working directory for running the application?
In the (managed service) Docker container, those files are located in /opt/shotover-proxy/config/.

On second thought, it might be preferable to leave the files and add some docs instead. 🤔

We should also rename all the config.yaml's in examples/

I didn't even realise they were named incorrectly. Definitely.

[rukai]

Replaced by this PR which has access to CI due to the branch being on shotover/shotover-proxy instead of my fork #117