Implement basic DynamoDB API adapter

[bootjp]

Summary

• add DynamoDB-compatible HTTP server supporting PutItem and GetItem
• translate DynamoDB JSON requests into internal operations
• test DynamoDB adapter using AWS SDK DynamoDB client and update test harness

Testing

• go test ./...
• go test -race ./... (fails: TestRbMemoryStore_TTL)
• golangci-lint --config=.golangci.yaml run --fix

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https://chatgpt.com/codex/tasks/task_e_68977637c0f88324922ae3a2af7b1776

[Copilot]

Pull Request Overview

This PR adds a DynamoDB-compatible HTTP API adapter to elastickv, enabling it to serve as a local DynamoDB substitute for testing and development purposes.

• Implements a DynamoDB HTTP server supporting PutItem, GetItem, UpdateItem, and TransactWriteItems operations
• Adds a transcoder to convert DynamoDB JSON requests into internal key-value operations
• Integrates the DynamoDB server into the test harness alongside existing gRPC and Redis servers

Reviewed Changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
go.mod	Adds AWS SDK for Go dependency
adapter/test_util.go	Extends test infrastructure to include DynamoDB server setup and port management
adapter/dynamodb_transcoder.go	Implements conversion from DynamoDB JSON format to internal operation format
adapter/dynamodb_test.go	Provides comprehensive test coverage for DynamoDB API operations
adapter/dynamodb.go	Core DynamoDB HTTP server implementation with request handling and condition validation

[Copilot]

The attributeValue struct only supports string values (S field), but DynamoDB supports multiple data types (N for numbers, B for binary, etc.). This limits the adapter's compatibility with real DynamoDB usage.

Suggested change

	S string `json:"S"`
	S *string `json:"S,omitempty"`
	N *string `json:"N,omitempty"`
	B *[]byte `json:"B,omitempty"`
	SS *[]string `json:"SS,omitempty"`
	NS *[]string `json:"NS,omitempty"`
	BS *[][]byte `json:"BS,omitempty"`
	BOOL *bool `json:"BOOL,omitempty"`
	NULL *bool `json:"NULL,omitempty"`
	L *[]attributeValue `json:"L,omitempty"`
	M *map[string]attributeValue `json:"M,omitempty"`