feat: v25 upgrade

[mlwelles]

Summary

Upgrades dgraph4j from v24.2.0 to v25.0.0, bringing full parity with the Dgraph v25 API.

New APIs

• RunDQL — run DQL queries and mutations directly without managing transactions
• ID Allocation — allocateUIDs(), allocateTimestamps(), allocateNamespaces()
• Namespace Management — createNamespace(), dropNamespace(), listNamespaces()
• Convenience Methods — dropAll(), dropData(), dropPredicate(), dropType(), setSchema()

All methods available on both DgraphAsyncClient (returning CompletableFuture<T>) and DgraphClient (sync wrapper).

Typed Exception Hierarchy

All exceptions now extend DgraphException (which extends StatusRuntimeException), with isRetryable() on every subclass. Existing catch (StatusRuntimeException e) blocks continue to work.

DgraphException (extends StatusRuntimeException)
├── AlphaException [retryable] — server reachable but temporarily unable to serve
│   ├── AlphaNotReadyException — startup, indexing, Raft init
│   ├── AlphaShutdownException — draining mode, try a different node
│   └── AlphaOverloadedException — too many pending requests
├── ConnectionException [retryable] — network-level, server unreachable
├── DeadlineExceededException [retryable] — operation timed out
├── TxnException
│   ├── TxnConflictException [retryable] — transaction conflict
│   ├── TxnFinishedException — transaction already committed/discarded
│   └── TxnReadOnlyException — mutation on read-only transaction
├── ResourceExhaustedException — e.g., gRPC message size limit
├── QueryException — invalid query/mutation syntax
├── DisallowedOperationException — server config blocks the operation
└── AuthException — authentication or authorization failure

Exceptions utility class centralizes translation from gRPC status codes to typed exceptions. ExceptionUtil retained as deprecated alias for backward compatibility.

Automatic Retry

withRetry() on both DgraphClient and DgraphAsyncClient provides managed transaction retry with exponential backoff:

Response resp = client.withRetry(txn -> {
    txn.mutate(mutation);
    txn.commit();
    return txn.query(query);
});

Configurable via RetryPolicy with support for read-only and best-effort transactions:

client.withRetry(RetryPolicy.bestEffort(), txn -> txn.query(query));

client.withRetry(RetryPolicy.builder()
    .maxRetries(10)
    .baseDelay(Duration.ofMillis(200))
    .build(), txn -> { ... });

Async variant uses non-blocking backoff via CompletableFuture.delayedExecutor.

Internal Refactoring

• CompletableFutures utility class — extracted runWithRetries (JWT-refresh retry) and attemptAsync (managed transaction retry with backoff) from DgraphAsyncClient into a stateless static utility class, keeping the async client focused on the Dgraph API surface
• Updated CODEOWNERS from @rarvikar to @mlwelles

Other Changes

• Updated proto definitions to Dgraph v25 (8 new RPCs)
• Updated copyright from Hypermode Inc. to Istari Digital, Inc.
• Updated GitHub org references from hypermodeinc to dgraph-io
• Deprecated clientStubFromSlashEndpoint / clientStubFromCloudEndpoint (now throw UnsupportedOperationException with migration guidance)
• Fixed isJwtExpired() to handle UNKNOWN status code
• Fixed 5 broken docs.dgraph.io links to match new site structure
• Updated README with new API documentation sections
• Updated CHANGELOG, samples, and CI workflows

Deprecated

• clientStubFromSlashEndpoint() — throws UnsupportedOperationException, use clientStub() instead
• clientStubFromCloudEndpoint() — throws UnsupportedOperationException, use clientStub() instead
• ExceptionUtil — use Exceptions instead

Removed

• Cloud-related documentation section from README

Test plan

• Integration tests pass against a 3-alpha + 1-zero Dgraph cluster with ACL enabled
• 3 new unit test classes: ExceptionHierarchyTest, ExceptionMappingTest, RetryPolicyTest
• All pre-existing tests continue to pass
• ./gradlew clean generateProto compileJava succeeds
• Trunk linter passes
• testDropType fixed — added dropAll() for clean schema state before type creation

---

Closes #283

[matthewmcneely]

Also, and this is a big one, Istari legal want the copyright header to read

/*
 * SPDX-FileCopyrightText: © 2017-2026 Istari Digital, Inc.
 * SPDX-License-Identifier: Apache-2.0
 */