subgraph schema push/registration

[n1ru4l]

Goal

Allow users to check or push a named subgraph version once and later publish that exact version without locating and uploading the SDL again.

The intended workflow is:

# Check the SDL and make products@$GIT_SHA available for publication.
hive schema:push schema.graphql \
  --service "products@$GIT_SHA" \
  --project my-org/my-project

# Publish the exact checked SDL later without passing the file again.
hive schema:publish \
  --service "products@$GIT_SHA" \
  --target my-org/my-project/production

This separates producing a subgraph schema from publishing it into a target. The registry guarantees that a version always identifies the same SDL, while the normal publish pipeline still performs composition, policy, contract, and artifact processing against the destination target's current state.

User-Facing Changes

Push subgraph without checking/publishing

Users can explicitly push/register SDL to the schema registry:

hive schema:push schema.graphql \
  --service products@1.4.0 \
  --project my-org/my-project

Registration stores the SDL for later use but does not change any target's published schema.

Publish a version

Users publish a registered version by omitting the schema file and including the version in the
service reference:

hive schema:publish \
  --service products@1.4.0 \
  --target my-org/my-project/production

The existing file-based publish remains supported:

hive schema:publish schema.graphql \
  --service products \
  --url https://products.example.com/graphql

Supplying both a schema file and service@version is ambiguous and rejected.

Handle an existing version

Versions are immutable from the user's perspective:

• Registering the same service, version, and SDL again succeeds idempotently.
• Registering the same service and version with different SDL fails with a conflict.
• Correcting a version normally requires choosing a new version name.
• Mutable names such as candidate or latest are out of scope of this task

An example conflict is:

Version products@1.4.0 already exists with a different schema.
Existing digest:  hive-sdl-v1:sha256:abc...
Submitted digest: hive-sdl-v1:sha256:def...

Design Guarantees

• The registry assigns an immutable digest based on canonical SDL.
• A user-provided version is an immutable alias for one digest.
• Versions can be reused across targets in the same project.
• Registration does not modify published target state.
• Publishing by reference executes the existing publish pipeline.
• Published history records the resolved SDL revision and service URL.