Add credential-free sample mode with sample data, README, and doc reconciliation

internal/auth/auth.go

@@ -39,6 +39,12 @@ func Email(r *http.Request) string {
 	return email
 }
 
+func Fixed(email string, next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		next.ServeHTTP(w, r.WithContext(context.WithValue(r.Context(), contextKey{}, email)))
+	})
+}
+
 func (a *Auth) Register(mux *http.ServeMux) {
 	mux.HandleFunc("POST /auth/login", a.login)
 	mux.HandleFunc("POST /auth/logout", a.logout)

internal/directory/cache.go

@@ -11,15 +11,19 @@ import (
 
 const refreshInterval = 5 * time.Minute
 
+type Geocoder interface {
+	Lookup(address string) (geocode.Point, error)
+}
+
 type Cache struct {
 	source   data.Source
-	geocoder *geocode.Client
+	geocoder Geocoder
 	blobs    BlobChecker
 	mu       sync.RWMutex
 	model    *Model
 }
 
-func NewCache(source data.Source, geocoder *geocode.Client, blobs BlobChecker) (*Cache, error) {
+func NewCache(source data.Source, geocoder Geocoder, blobs BlobChecker) (*Cache, error) {
 	c := &Cache{source: source, geocoder: geocoder, blobs: blobs}
 	if err := c.refresh(); err != nil {
 		return nil, err

internal/geocode/fake.go

@@ -0,0 +1,13 @@
+package geocode
+
+import "crypto/sha256"
+
+type Fake struct{}
+
+func (Fake) Lookup(address string) (Point, error) {
+	sum := sha256.Sum256([]byte(address))
+	return Point{
+		Lat: 37.5 + (float64(sum[0])/255-0.5)*0.12,
+		Lng: -122.45 + (float64(sum[1])/255-0.5)*0.12,
+	}, nil
+}