feat(core): add support for ssh connections into sessions

[Panaetius]

closes #3293
closes #3289
closes #3290

/deploy #persist renku-notebooks=master extra-values=notebooks.ssh.enabled=true,notebooks.ssh.service.type=NodePort,notebooks.ssh.service.port=32023

[coveralls]

Pull Request Test Coverage Report for Build 4261590825

• 359 of 434 (82.72%) changed or added relevant lines in 34 files are covered.
• 34 unchanged lines in 13 files lost coverage.
• Overall coverage increased (+0.3%) to 86.873%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
renku/command/format/session.py	1	2	50.0%
renku/core/session/utils.py	2	3	66.67%
renku/core/util/ssh.py	75	77	97.4%
renku/infrastructure/repository.py	4	6	66.67%
renku/ui/cli/session.py	24	26	92.31%
renku/ui/service/views/v1/templates.py	15	18	83.33%
renku/core/errors.py	5	9	55.56%
renku/core/session/session.py	53	57	92.98%
renku/domain_model/session.py	13	17	76.47%
renku/core/session/docker.py	10	16	62.5%

Files with Coverage Reduction	New Missed Lines	%
renku/core/dataset/dataset.py	1	91.18%
renku/core/login.py	1	83.97%
renku/core/template/template.py	1	87.02%
renku/core/util/tabulate.py	1	96.3%
renku/core/workflow/activity.py	1	93.89%
renku/domain_model/project_context.py	1	96.37%
renku/domain_model/workflow/composite_plan.py	1	81.55%
renku/ui/service/controllers/datasets_add_file.py	1	95.24%
renku/ui/service/jobs/contexts.py	1	73.33%
renku/version.py	2	75.0%

Totals
Change from base Build 4234036165:	0.3%
Covered Lines:	25427
Relevant Lines:	29269

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💛 - Coveralls

[RenkuBot]

You can access the deployment of this PR at https://renku-ci-rp-3318.dev.renku.ch

[Panaetius]

Basically we created the keypair and pushed - so now, by definition, the image is building - but we tell the user "image is not there, would you like to build it with Renkulab?"

No, when it asks you this, the keypair is added, but not pushed. So, by definition, it isn't building yet

This code is provider independent, so this code is executed with docker and renkulab sessions

Why can't I connect with ssh to a session that I started in the UI?

That's added now

this sort of hostname is... big! renku-ci-rp-3318.dev.renku.ch-test-session-ssh-rokroskar--test-2dsession-2dssh-5c3af687 Why can't we make it shorter? A config like this works fine:

The original thinking was that this way you can distinguish what deployment a session is on based on the name, but since most users won't be on more than 1 deployment anyways, that's now a hard requirement.
One technical reason is that we have automated garbage collection based on the connection name (removing old connection configs if the corresponding session isn't running anymore) and that uses the connection name to identify the connections and I didn't want to delete SSH connections from other deployments just because we can't find them on the current deployment. We could probably also do that through the filename instead of through the connection name.
It's a bit of a leftover from before I realized that Include ... works well with many files, when I didn't want to litter a users SSH config with too much stuff, so the Wildcard match entry deduplicated a lot of the clutter.
If we want to change this then I would just use the session ID as connection name directly instead of having two different identifiers.

[rokroskar]

I found two questionable doc strings... 😆