feat: migrate to new embedded Dgraph client and add validation support

[matthewmcneely]

Description

Major refactoring to replace the old embedded server implementation with the new
Dgraph v25 embedded client architecture, providing better performance and
stability for in-process deployments.

Breaking Changes:

• Replaced buf_server.go with new embedded_client.go implementation
• Updated all import paths from github.com/hypermodeinc/dgraph to github.com/dgraph-io/dgraph
• Client initialization now uses the new embedded client architecture

New Features:

• Add comprehensive validation support using github.com/go-playground/validator/v10
• New WithValidator() client option for custom validation rules
• Validation integrated into Insert, Update, and Upsert operations
• Support for custom validation functions and struct tags

Enhanced Test Coverage:

• Added validate_test.go with comprehensive validation test suite
• Enhanced update_test.go and upsert_test.go with more test cases
• Improved error handling and edge case testing
• Added tests for custom validation rules and partial validation failures

Dependency Updates:

• Updated Dgraph dependencies to v25 stable release
• Upgraded Go modules to latest stable versions
• Updated gRPC to v1.78.0 for better performance
• Refreshed all indirect dependencies for security and stability

Performance Improvements:

• Optimized embedded client connection handling
• Improved mutation performance with better error handling
• Enhanced query execution with the new embedded client

Bug Fixes:

• Fixed import paths for Dgraph v25 compatibility
• Resolved connection issues in embedded mode
• Improved error messages for validation failures
• Fixed test cases that were assuming order in assertions

Documentation:

• Updated README.md with new embedded client usage examples
• Clarified connection string formats for file vs Dgraph URIs
• Added validation examples and best practices

This migration provides a more stable foundation for embedded deployments
while maintaining full backward compatibility for remote Dgraph connections.

Checklist

• Code compiles correctly and linting passes locally
• For all code changes, an entry added to the CHANGELOG.md file describing and linking to
  this PR
• Tests added for new functionality, or regression tests for bug fixes added as applicable

---

Summary by cubic

Migrates embedded mode to the Dgraph v25 embedded client for faster, more stable in-process use, and adds entity validation via WithValidator across insert, update, and upsert. Updates to the latest Dgraph v25 build and refreshes README docs.

• New Features

  • Embedded client for file:// URIs; seamless with remote clients.
  • Validation using go-playground/validator; custom rules and tags; enforced on insert/update/upsert.
  • Clearer unique constraint errors mapped to UniqueError.

• Migration

  • Imports switched to github.com/dgraph-io/dgraph; removed bufconn-based server.
  • file:// now auto-uses the embedded client; remote Dgraph connections are unchanged.
  • Bumped Dgraph v25 dependency and updated README links and WithValidator example.

^{Written for commit 20b9f97. Summary will update on new commits.}

[cubic-dev-ai]

3 issues found across 34 files

Prompt for AI agents (all issues)

Check if these issues are valid — if so, understand the root cause of each and fix them.


<file name="engine.go">

<violation number="1" location="engine.go:553">
P2: The `commitOrAbort` function always uses `engine.db0` (default namespace) instead of the namespace associated with the transaction. When `embeddedDgraphClient.CommitOrAbort` calls this method, the client's namespace (`c.ns`) is ignored, which could cause commits to target the wrong namespace in multi-namespace scenarios.</violation>
</file>

<file name="README.md">

<violation number="1" location="README.md:165">
P3: The heading lists `WithValidator(Validator)`, but the API expects a `StructValidator` (or *validator.Validate implementing it). This mismatch can mislead users about the correct type. Rename the heading to match the actual interface.</violation>
</file>

<file name="client.go">

<violation number="1" location="client.go:276">
P2: Ignoring errors from `engine.GetNamespace` can leave `ns` nil, which will panic when the embedded client calls `c.ns.ID()` for an invalid/unknown namespace. Return the namespace lookup error instead of discarding it.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[cubic-dev-ai]

1 issue found across 6 files (changes from recent commits).

Prompt for AI agents (all issues)

Check if these issues are valid — if so, understand the root cause of each and fix them.


<file name="client_test.go">

<violation number="1" location="client_test.go:444">
P3: The test only asserts when err != nil, so invalid namespaces can pass silently if NewClient returns nil. Always assert an error (after handling the singleton skip) to avoid false negatives.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}