Added
- New crate `kamu-adapter-graphql` provides GraphQL interface for ODF repositories.
- New command `kamu system api-server` runs HTTP + GraphQL server over current Kamu workspace with built-in GQL Playground UI.
- New command `kamu system api-server gql-query` executes single GraphQL query and writes JSON output to stdout.
- New command `kamu system api-server gql-schema` dumps GraphQL API schema to stdout.