feat(backend): Add configuration to conditionally disable shared pipeline resources

[krishanbhasin-px]

Description of your changes:
This PR will add a new configuration option for Kubeflow to optionally disable the ability to upload pipelines to the "shared" space (achieved by setting namespace to None/"").

This config will default to the same behaviour as right now (allowing shared pipelines) so this should not be a breaking change for existing users.

I was curious about the possibility of even doing this which is why I started drafting the code change up front.

I have now opened this PR early to share the idea; if you are open to merging this change I can implement the relevant tests and any other bits that are needed in order to get this in.

I summarised the problem I am trying to solve with this in the CNCF Slack group; I've copied the important bits below:

problem statement

I'm working in an environment where we want to deploy Kubeflow in a multi-tenant way; where I can isolate access to each tenant based on the authorisation of the logged in user.
For example I have a single Kubeflow instance, with 3 tenants that need to use it - "Project A", "Project B", and "Project C".

Alice and Alex work on A, Bob works on B, and Charlie works on C. Users that work on a particular project should not have access to resources for an other project.

To implement this, I have created KubeFlow Profiles for "Proj-A", "Proj-B", and "Proj-C". As the notebook instances within those profiles don't have access controls (and after reading previous threads on this matter), I have also created "child" profiles for each of my users - "Alice-A", "Alex-A", "Bob-B", "Charlie-C". So Alice has access to "Proj-A" and "Alice-A" (and the rest follow similarly)

I had hoped to have each user work in notebooks in their private profiles and, once they have created a pipeline that they think is worth using longer-term, they "publish" it to the project's main profile.

In my testing of this setup I have realised that:

1. I can't find a way to allow a notebook in profile "Alice-A" to upload/publish a pipeline to "Proj-A"'s private pipeline space
   • I solved this with the kind guidance of Julius von Kohout
2. They can upload to the Shared space (by setting namespace=None in the upload API call), but unfortunately, any profile in the kubeflow instance can access them - I want to avoid this possibility (whether done by accident or otherwise).

Checklist:

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[google-oss-prow]

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[google-oss-prow]

Hi @krishanbhasin-px. Thanks for your PR.

I'm waiting for a kubeflow member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[rimolive]

/ok-to-test

[rimolive]

@krishanbhasin-px Please rebase your PR

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Approvals successfully granted for pending runs.

[HumairAK]

@krishanbhasin-px thanks for the pr, could you address the ci failures? feel free to ping me in slack for another look if I miss the re-review

[krishanbhasin-px]

@HumairAK happily! Can I take this as confirmation that you/the team is happy with the intent of this PR? I wanted to get a confirmation before I put time into preparing it 'properly'