refactor: move lava contracts to pkg/lava (#118)

[kooksee]

Summary

• Move Request/Response/Middleware/router interfaces from module root lava/ to pkg/lava/.
• Update all internal imports to github.com/pubgo/lava/v2/pkg/lava.
• Keep root lava/ as a deprecated type-alias shim for external backward compatibility.

Closes #118

Notes

• pkg/lava/router.go still references fiber/gRPC types; further decoupling can be a follow-up.

Test plan

• go test ./... -race -short
• golangci-lint run ./lava/... ./pkg/lava/...

Made with Cursor

[gemini-code-assist]

Code Review

This pull request moves the core contracts and interfaces of the lava package to a new location under pkg/lava, updating all internal import paths accordingly. To maintain backward compatibility, a deprecated lava package is introduced in lava/doc.go that re-exports the public API. Feedback was provided to avoid re-exporting package-level functions as mutable variables (var) in lava/doc.go, suggesting instead to use wrapper functions to prevent accidental or malicious overwrites.

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[gemini-code-assist]

Re-exporting package-level functions as mutable variables (var) allows external code or dependencies to accidentally or maliciously overwrite them (e.g., lava.Chain = nil). To prevent this and ensure safety, it is highly recommended to re-export them as wrapper functions instead.

Suggested change

	var (
	WithMiddleware = plava.WithMiddleware
	Chain = plava.Chain
	)
	func WithMiddleware(name string, next func(next HandlerFunc) HandlerFunc) MiddlewareWrap {
	return plava.WithMiddleware(name, next)
	}
	func Chain(middlewares ...Middleware) Middleware {
	return plava.Chain(middlewares...)
	}