Deprecations for v2 upgrades

[minrk]

Adds deprecated aliases for the APIs that were removed in #145

should prevent unnecessary breakage while folks upgrade

closes #149

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Deprecations

TraefikConsulProxy class

• kv_url is deprecated, use consul_url
• kv_username is deprecated, use consul_username
• kv_password is deprecated, use consul_password

TraefikEtcdProxy class

• kv_url is deprecated, use etcd_url
• kv_username is deprecated, use etcd_username
• kv_password is deprecated, use etcd_password

TraefikTomlProxy class

• The class is deprecated, use TraefikFileProviderProxy instead
• toml_dynamic_config_file is deprecated, use dynamic_config_file instead. YAML is also supported.

TraefikProxy class (all classes)

• toml_static_config_file is deprecated, use static_config_file. YAML is also supported.

[minrk]

I removed these generic traits from KVProxy which weren't actually generic - these are unused by the base class and not actually general, even though our two subclasses have sufficiently similar setups.

I traded them for more descriptive and specific etcd_username, etc. config on the specific implementation classes, since these should be implementation-specific details, not generic features.

[GeorgianaElena]

Thank you @minrk

[GeorgianaElena]

The etcd tests seem to have hanged as they run from over an hour and didn't finish :/

[consideRatio]

I cancelled the etcd workflow that kept running now, 4 hours in.

[consideRatio]

Besides having a test issue that needs to be addressed, this LGTM! I also figured its useful to have the deprecations listed in the PR description, so I added what I understand them to be so please review that edit I made also.

Resolve or understand the test hanging to be unrelated and this LGTM!

[minrk]

Thanks! Hang was the result of merging a few test changes, seems to be all good now.

[alexleach]

There's still a run in progress actually, been going 5 hours and counting: https://github.com/jupyterhub/traefik-proxy/actions/runs/4241217403