graphql: implement changes subscription

api/graphql/graph/root_.generated.go

api/graphql/graph/subscription.generated.go

api/graphql/handler.go

api/graphql/models/gen_models.go

api/graphql/models/lazy_bug.go

api/graphql/resolvers/root.go

api/graphql/resolvers/subscription.go

api/graphql/schema/subscription.graphql

cache/filter.go

cache/repo_cache.go

cache/subcache.go

entities/bug/bug.go