UI API Layer module pluggability

[pkosiec]

Description

Implement module pluggability for UI API Layer, according to the accepted proposal: kyma-project/community#141

Documentation

• Create decision log for UI API Layer modularization concept (issue: Prepare UI API Layer modularization concept #1721, proposal: Create UI API Layer modularization proposal community#141)
• Document ui-api-layer in Console topic in Kyma docs by explaining its purpose and scope, modularity and provide new CRD reference docs (https://github.com/kyma-project/community/blob/master/guidelines/templates/resources/custom-resource.md)

UI API Layer

• Create custom resource and generate Informer API for it
• Fork and modify https://github.com/josharian/impl to always return error for every method - PK: impl won't fit there, https://github.com/vektra/mockery will be a better pick
• Implement production-ready module pluggability in UI API Layer based on PoC Prepare UI API Layer Modularization PoC #1849. Hide it behind feature flag. Sync with @Abd4llA and his proposal Add a proposal for feature introduction through feature gates and installer profiles community#92 to do the feature flag properly
• Make all domain modules pluggable
• Make necessary modifications in UI API Layer acceptance tests
• Split servicecatalog module to servicecatalog and servicecatalogaddons
• Create BackendModule custom resources in Kyma components

Console UI

• Set up a meeting with UI teams to show how to make resilient UIs, when some UI API Layer modules are turned off. Prepare example of modularity in the Service Catalog UI
• Review all Console UI views - which crash when a module is not available. Prepare a list and working cluster. Best would be to do a pull request with such simulation. Remember about UI tests in the demo

Reasons

UI API Layer exposes GraphQL API for the Kyma Console. It consists of resolver logic for different domains, like Kubernetes, Service Catalog, Remote Environments, Kubeless, etc. As Kyma needs to be modularized, users should be able to install only the components they need.

The current approach we use in UI API Layer makes it impossible. During the GraphQL server start, we try to synchronize Stores of all Informers. As a result, if a resource of a specific type doesn't exist, UI API Layer won't start properly because its Informer will return an error.

[pkosiec]

Please consider using GraphQL directives: https://gqlgen.com/reference/directives/

[mjasinski5]

Review: @michal-hudy

[mjasinski5]

#2084 Review: @michal-hudy