feat: allow data connectors to be skipped when launching sessions

[leafty]

Closes #1009.

⚠️ Includes API breaking changes ⚠️

Allows data connectors to be skipped when launching a session.

UI update: SwissDataScienceCenter/renku-ui#3873.

Note: more related changes can be found in #1068.

/deploy renku-ui=leafty/feat-allow-dc-skip

[RenkuBot]

You can access the deployment of this PR at https://renku-ci-ds-1065.dev.renku.ch

[coveralls]

Pull Request Test Coverage Report for Build 18707793088

Details

• 36 of 59 (61.02%) changed or added relevant lines in 4 files are covered.
• 5 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.006%) to 86.825%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
components/renku_data_services/notebooks/blueprints.py	0	1	0.0%
components/renku_data_services/notebooks/core_sessions.py	4	26	15.38%

Files with Coverage Reduction	New Missed Lines	%
components/renku_data_services/notebooks/blueprints.py	1	76.84%
components/renku_data_services/data_connectors/doi/metadata.py	2	70.67%
components/renku_data_services/notebooks/core_sessions.py	2	17.39%

Totals
Change from base Build 18690049033:	0.006%
Covered Lines:	22723
Relevant Lines:	26171

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💛 - Coveralls

[olevski]

Thanks Flora. Just 2 small changes to remove leftover stuff from developing this.

[RenkuBot]

Tearing down the temporary RenkuLab deployment for this PR.