Allow selecting installed optional dependencies in Docker build

[juhoinkinen]

Currently we provide a Dockerfile and an image in quay.io with dependencies for all the optional features.

If someone does not need all the features, but e.g. uses only Omikuji backend and would like build their own image (e.g. for smaller size), they could edit the Dockerfile dropping the unwanted (Python) dependencies from the pip install command. However, using --build-arg option of docker build provides a way to pass the user-defined list of dependencies to install that overrides the default list:

docker build -t annif-omikuji-voikko --build-arg optional_dependencies=omikuji,voikko .

A user wanting to have a Docker image to use with Xtransfomer could add pecos to the default list in build time.

[codecov]

Codecov Report

Merging #548 (38adcf8) into master (5c6af91) will not change coverage.
The diff coverage is n/a.

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  Files          80       80           
  Lines        5313     5313           
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  Hits         5286     5286           
  Misses         27       27           

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[osma]

What about fasttext? It will be installed regardless of this setting, right?

[juhoinkinen]

What about fasttext? It will be installed regardless of this setting, right?

Yes, that's true, I thought it would not be installed... Or at least not available right away. Hmm, I don't if its copying from builder stage can be controlled this way conveniently enough.

[osma]

I don't think always including fasttext is a very big deal, this PR is still a big improvement.

That said, I think it could be possible to avoid installing fasttext by making the pip install command on line 9 conditional. Something like:

if [[ $optional_dependencies =~ "fasttext" ]]; then pip install --no-cache-dir fasttext==0.9.2; fi

(perhaps the apt-get install build-essential command could be moved inside the if clause as well, to avoid doing useless extra work in case fasttext isn't needed)

The ARG declaration needs to be moved earlier of course.

The COPY command would then copy an empty /usr/local/lib/python3.8 directory from the builder image.

[sonarcloud]

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[osma]

LGTM

[juhoinkinen]

I added a section of customizing Docker image to Wiki: https://github.com/NatLibFi/Annif/wiki/Usage-with-Docker#customizing-docker-image