Add docflex/Raft-Consensus (Java) to implementations

[docflex]

Description:

Adds Raft-Consensus — a Java 21 implementation of Raft built with Spring Boot and gRPC.

Implementation Details

• Language: Java 21 (Spring Boot 3.2, gRPC 1.62)
• License: MIT
• Features:
  • Leader election with pre-vote (§3.4, §9.6)
  • Log replication & consistency checking (§3.5)
  • Durable persistence via RiptideKV, a custom embedded KV engine with WAL-based durability and SSTable compaction (§3.1)
  • Dynamic membership changes — single-server (§4)
  • Log compaction via snapshots + InstallSnapshot RPC (§7)
  • Linearizable reads (readIndex protocol) (§6.4)
  • Client command deduplication (§6.3)

Test Coverage

191 tests covering unit, integration, and stress scenarios.