schema: add source workflows

[oliver-sanders]

Add source workflows to the schema.

Unblocks cylc/cylc-ui#548, though we will probably want to extend this to subscriptions for that.

Check List

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[dwsutherland]

Looks fine, tests passing.
Probably would need to create this on the cylc-flow end to add to subscriptions (which might make more sense, as field(s) in a data-store).

[hjoliver]

Is that a formal review/approval @dwsutherland ?

[oliver-sanders]

Getting this into subscriptions would make sense, making it easier for cylc-ui views to access this information.

Would we have to add these fields in cylc-flow or could we shim them into cylc-uiserver similar to how we extend the GraphQL schema?

[dwsutherland]

Would we have to add these fields in cylc-flow or could we shim them into cylc-uiserver similar to how we extend the GraphQL schema?

Well, if we add this to the cylc-flow schema then:

• it will be available both ends (schd and UIS)
• we may not need to figure it out if the Scheduler already knows (i.e. the resolver code here)
• and if it's a workflow field of the data-store, then it's automatically in the subscriptions

[oliver-sanders]

Because this is UIS specific functionality that the Scheduler should never know about it would be better to try and keep this logic centralised in cylc-uiserver. Is is possible to extend the protobuf schema in a similar way to how we extend the GraphQL schema?

[dwsutherland]

Ah, so it's not about knowing the source of installed/running workflows, it's about knowing cylc-src or it's aliases...

Yeah, better to keep it at UIS then, and we shouldn't need to deal with protobuf .. can just extend the subscriptions at the UIS

[oliver-sanders]

Ok, I'll look into doing that. Would it be possible to extend the store to hold this or would I need to add a parallel store?

[oliver-sanders]

(may as well draft this until the fields are available in subscriptions)