UI Extension: support multiple PromotionStrategies w/ direct links

[seanl-circle]

I had the ui extension installed in argocd-server as described in https://argo-cd.readthedocs.io/en/stable/developer-guide/extensions/ui-extensions/#ui-extensions

In 0.18.2 it works, and there's a promotionstrategy tab on promotionstrategy resources
In 0.18.3 / 0.19.0 it just doesn't show up at all. I couldn't find any errors or logs from argocd-server or in the browser console logs.

[zachaller]

I think we just moved it, you can click the little branching like icon:

[seanl-circle]

Hmm, that might be a bit of a problem for us.
We have repos that can can hold either a single or multiple services, and each may have one or more instances deployed independently.

Our plan was to use the an appset with an scm generator to map 1 repo to 1 root argocd application, which would for each service instance in that repo, template out a promotionstrategy + appset with a cluster generator.
So each root argocd application can hold multiple promotion strategies

Moving promotion strategy ui there it looks like it only supports one promotionstrategy per app?
The application screen crashes with:

Something went wrong!

Consider submitting an issue [here](https://github.com/argoproj/argo-cd/issues/new?labels=bug&template=bug_report.md).


Stacktrace:

Error: Expected exactly one PromotionStrategy resource in Gitops Promoter Extension, found 2
    at window.extensionsAPI.registerAppViewExtension.t (https://argocd-staging.example.com/extensions.js:2:42499)
    at Qo (https://argocd-staging.example.com/main.b8f3b898a503e41b9e16.js:2:563114)
    at Es (https://argocd-staging.example.com/main.b8f3b898a503e41b9e16.js:2:609072)
    at kl (https://argocd-staging.example.com/main.b8f3b898a503e41b9e16.js:2:601856)
    at xl (https://argocd-staging.example.com/main.b8f3b898a503e41b9e16.js:2:601781)
    at hl (https://argocd-staging.example.com/main.b8f3b898a503e41b9e16.js:2:598814)
    at https://argocd-staging.example.com/main.b8f3b898a503e41b9e16.js:2:550534
    at t.unstable_runWithPriority (https://argocd-staging.example.com/main.b8f3b898a503e41b9e16.js:2:625639)
    at Va (https://argocd-staging.example.com/main.b8f3b898a503e41b9e16.js:2:550243)
    at Ja (https://argocd-staging.example.com/main.b8f3b898a503e41b9e16.js:2:550479)

[crenshaw-dev]

Moving promotion strategy ui there it looks like it only supports one promotionstrategy per app?

It does currently, but imo we should probably add a dropdown and support multiple. Would that UX be good for your use case?

[seanl-circle]

As long as I can select the right one by constructing the appropriate url.
In our pull request template we include links to the ui, we'll also link to it from elsewhere.