Progressive overrides are a safer way to handle migrations. This feature should be implemented in the gateway.

• https://www.apollographql.com/docs/graphos/schema-design/federated-schemas/reference/directives#progressive-override
• https://www.apollographql.com/docs/graphos/schema-design/federated-schemas/entities/migrate-fields#customizing-progressive-override-behavior-with-a-feature-flag-service

Proposed Feature Set:

• Ability to parse labelspercentage(<integer/float>) numbers and apply them for subgraphs
• Ability to warn about unknown override labels and resolve them via plugin
  • see https://www.apollographql.com/docs/graphos/schema-design/federated-schemas/entities/migrate-fields#customizing-progressive-override-behavior-with-a-feature-flag-service)
  • see https://github.com/graphql-hive/router/blob/704a112e8486fded3b558609f8e0d190d74f57ce/lib/query-planner/src/tests/overrides.rs#L331-L379

Related issues:

• Composition for @override directive federation-composition#84