feat!: introduce logger choice via slog

Historically brokerapi has required use of the
[`lager`](https://github.com/cloudfoundry/lager) logger. In Go 1.21,
structured logging was introduced into the Go standard library via the
[`log/slog`](https://pkg.go.dev/log/slog) package, and `slog`
[compatability was added](cloudfoundry/lager@4bf4955)
to `lager`.

`brokerapi` has been modified to require a `slog` logger to be passed
rather than a `lager` logger. This allows users a choice of logger.
Users who still want to use lager can easily do that using the
lager/slog compatability:
```go
logger := lager.NewLogger(name)
brokerAPI := brokerapi.New(serviceBroker, slog.New(lager.NewHandler(logger)), credentials)
```

And users who want to use `slog` or an `slog`-compatible logger can do
that instead.

A key advantage is that `lager` is no longer a dependency of this
package, which simplifies package management for apps that use brokerapi
and other libraries which use `lager`.

Author: blgm

.github/workflows/run-tests.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        version: [ 'stable', 'oldstable', '1.20' ]
+        version: [ 'stable', 'oldstable', '1.21' ]
     name: Go ${{ matrix.version }}
     outputs:
       pr_number: ${{ github.event.number }}

api.go

@@ -16,9 +16,9 @@
 package brokerapi
 
 import (
+	"log/slog"
 	"net/http"
 
-	"code.cloudfoundry.org/lager/v3"
 	"github.com/go-chi/chi/v5"
 	"github.com/pivotal-cf/brokerapi/v10/handlers"
 )
@@ -28,19 +28,19 @@ type BrokerCredentials struct {
 	Password string
 }
 
-func New(serviceBroker ServiceBroker, logger lager.Logger, brokerCredentials BrokerCredentials) http.Handler {
+func New(serviceBroker ServiceBroker, logger *slog.Logger, brokerCredentials BrokerCredentials) http.Handler {
 	return NewWithOptions(serviceBroker, logger, WithBrokerCredentials(brokerCredentials))
 }
 
-func NewWithCustomAuth(serviceBroker ServiceBroker, logger lager.Logger, authMiddleware middlewareFunc) http.Handler {
+func NewWithCustomAuth(serviceBroker ServiceBroker, logger *slog.Logger, authMiddleware middlewareFunc) http.Handler {
 	return NewWithOptions(serviceBroker, logger, WithCustomAuth(authMiddleware))
 }
 
-func AttachRoutes(router chi.Router, serviceBroker ServiceBroker, logger lager.Logger) {
+func AttachRoutes(router chi.Router, serviceBroker ServiceBroker, logger *slog.Logger) {
 	attachRoutes(router, serviceBroker, logger)
 }
 
-func attachRoutes(router chi.Router, serviceBroker ServiceBroker, logger lager.Logger) {
+func attachRoutes(router chi.Router, serviceBroker ServiceBroker, logger *slog.Logger) {
 	apiHandler := handlers.NewApiHandler(serviceBroker, logger)
 	router.Get("/v2/catalog", apiHandler.Catalog)
 

api_options.go

@@ -16,9 +16,9 @@
 package brokerapi
 
 import (
+	"log/slog"
 	"net/http"
 
-	"code.cloudfoundry.org/lager/v3"
 	"github.com/go-chi/chi/v5"
 	"github.com/pivotal-cf/brokerapi/v10/auth"
 	"github.com/pivotal-cf/brokerapi/v10/domain"
@@ -27,7 +27,7 @@ import (
 
 type middlewareFunc func(http.Handler) http.Handler
 
-func NewWithOptions(serviceBroker domain.ServiceBroker, logger lager.Logger, opts ...Option) http.Handler {
+func NewWithOptions(serviceBroker domain.ServiceBroker, logger *slog.Logger, opts ...Option) http.Handler {
 	cfg := newDefaultConfig(logger)
 	WithOptions(append(opts, withDefaultMiddleware())...)(cfg)
 	attachRoutes(cfg.router, serviceBroker, logger)
@@ -70,7 +70,7 @@ func WithEncodedPath() Option {
 func withDefaultMiddleware() Option {
 	return func(c *config) {
 		if !c.customRouter {
-			c.router.Use(middlewares.APIVersionMiddleware{LoggerFactory: c.logger}.ValidateAPIVersionHdr)
+			c.router.Use(middlewares.APIVersionMiddleware{Logger: c.logger}.ValidateAPIVersionHdr)
 			c.router.Use(middlewares.AddCorrelationIDToContext)
 			c.router.Use(middlewares.AddOriginatingIdentityToContext)
 			c.router.Use(middlewares.AddInfoLocationToContext)
@@ -87,7 +87,7 @@ func WithOptions(opts ...Option) Option {
 	}
 }
 
-func newDefaultConfig(logger lager.Logger) *config {
+func newDefaultConfig(logger *slog.Logger) *config {
 	return &config{
 		router:       chi.NewRouter(),
 		customRouter: false,
@@ -98,5 +98,5 @@ func newDefaultConfig(logger lager.Logger) *config {
 type config struct {
 	router       chi.Router
 	customRouter bool
-	logger       lager.Logger
+	logger       *slog.Logger
 }