Feature/ext

[mike0sv]

Draft for interface for mlem/dvc integration

Fast test (preferable with iterative/mlem#169 mlem version):

python -c "import mlem; a = lambda x: x; mlem.api.save(a, 'model')"
gto describe model

[mike0sv]

tagging #46

[aguschin]

As mentioned by @shcheklein, when DVC is installed as binary, GTO may not be able to discover DVC Python API. We need to support CLI as a fallback then. As an option, we can list dvc and mlem in config file gto.yaml so GTO will know what to search for.

[mike0sv]

Added DVC integration implementation (as an example, it is actually stupid)
To test it you can run something like this

dvc init --subdir
echo "data" > file
dvc add file
gto describe file

[mike0sv]

Also added CLI implementation for the case we discussed. It will require for dvc/mlem to have special command that prints metadata, but you can test it like this
create a gto.yaml with this content:

enrichments:
  - type: cli
    config:
      cmd: "echo {\"size\":10,\"hash\":\"aa\"}"
      info_type: gto.ext_dvc.DVCEnrichmentInfo

and run gto describe ""
the "" is needed as argument but should be empty since it's content is added to the end of echo