Skip/include fixes

Fixes some bugs in the handling of skip/include selections that eliminate all selections for a scope. See #178.

API cleanups

See #176.

Does some cleanup to APIs so that the entire library can be driven using just a Client, and completely reorganizes documentation around this theme.

Visibility controls

Adds visibility controls to a stitched schema, allowing parts of a supergraph to be hidden from select audiences without compromising stitching implementation details. This offers the capabilities of Apollo Federation's @inaccessible directive with more flexibility atop GraphQL Ruby's Visibility system. See #173.

This is a pretty significant new feature, but has no breaking changes.

Restore `AlwaysVisible`

Restores AlwaysVisible (for schema performance), which was previously disabled for compatibility with GraphQL Ruby v2.5.3. This version works through several more realignments that match the new GraphQL Ruby Visibility system. See #171.

GraphQL v2.5.3 compatibility

Removes the use of GraphQL::Schema::AlwaysVisible, which was never strictly necessary and now is broken in recent versions of the GraphQL gem.

Fix request variable validations

Fixes request variable validations that were previously missing while integrating closer with GraphQL::Query. See #167.

GraphQL Ruby 2.4 compatibility

Mundane housekeeping to organize library and keep pace with GraphQL Ruby updates. Also fixes CI tests that were not actually running against minor versions of the GraphQL Ruby gem; drops support for GraphQL 1.13 which hasn't actually been compatible.

Fix abstract resolver mappings

• Fixes a bug with expanding abstract resolvers, per #157; see #158.
• Incorporates library version into all hashing digests; see #161.
• Allows digest library to be customized with faster alternatives such as Blake3; see #161.
• General library cleanup and refactoring, as tracked in #159.

Subscriptions support

Adds support for subscription operations in #152, with a Rails example in #153. Minimally disruptive API changes:

1. Stitching now returns a GraphQL::Query::Result rather than a raw hash, just like a standard GraphQL execution. If this causes problems in a test, call to_h on the result for the raw hash.

2. Stitching Client.execute can now be invoked with the query as a positional argument rather than a query: kwarg (for parity with GraphQL Ruby). The old kwarg is also still supported.

Fix planner key deduplication

Small updates from #150. Fixes the new key deduplication process from v1.4.0 that isn't compatible with fragments.