feat(tenants): provision the product tenant with the registry UUID on create (#21)

internal/product/product.go

@@ -0,0 +1,106 @@
+// Package product provisions a tenant into the downstream product database.
+//
+// The registry is the authority for tenant identity (ratified model B2), so a
+// product must anchor its own tenant row to the SAME canonical UUID. Without
+// this the anchors diverge: the registry knows "acme", the product database
+// does not, and the product's gate rejects every request from that tenant
+// because it cannot resolve the org slug.
+//
+// The Provisioner is a port, mirroring keycloak.Adapter: handlers depend on the
+// interface, main wires the HTTP implementation when PRODUCT_API_URL is set and
+// a no-op otherwise (dev convenience, and so an unconfigured deployment does
+// not fail tenant creation).
+package product
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"time"
+)
+
+// ErrUnavailable means the product API could not be reached or refused us.
+var ErrUnavailable = errors.New("product: provisioning API unavailable")
+
+// Tenant is the minimal identity a product needs to create its own row.
+type Tenant struct {
+	ID   string `json:"id"` // the registry UUID — the whole point
+	Name string `json:"name"`
+	Slug string `json:"slug"`
+}
+
+// Provisioner creates the tenant in a product's own datastore.
+type Provisioner interface {
+	ProvisionTenant(ctx context.Context, t Tenant) error
+}
+
+// NoopProvisioner is wired when PRODUCT_API_URL is unset.
+type NoopProvisioner struct{}
+
+func (NoopProvisioner) ProvisionTenant(context.Context, Tenant) error { return nil }
+
+// AuthHeaderFunc supplies an Authorization header per call, so a token is
+// fetched lazily and refreshed rather than captured at construction. Nil means
+// no header, which is the correct behaviour against a product whose gate is
+// not yet enforcing.
+type AuthHeaderFunc func(context.Context) (string, error)
+
+// HTTPProvisioner calls the product's tenant-create endpoint.
+type HTTPProvisioner struct {
+	BaseURL string
+	Path    string // e.g. /sdk/v1/tenants
+	Auth    AuthHeaderFunc
+	Client  *http.Client
+}
+
+func NewHTTPProvisioner(baseURL, path string, auth AuthHeaderFunc, timeout time.Duration) *HTTPProvisioner {
+	if path == "" {
+		path = "/sdk/v1/tenants"
+	}
+	return &HTTPProvisioner{
+		BaseURL: baseURL, Path: path, Auth: auth,
+		Client: &http.Client{Timeout: timeout},
+	}
+}
+
+func (p *HTTPProvisioner) ProvisionTenant(ctx context.Context, t Tenant) error {
+	body, err := json.Marshal(t)
+	if err != nil {
+		return err
+	}
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, p.BaseURL+p.Path, bytes.NewReader(body))
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Content-Type", "application/json")
+	if p.Auth != nil {
+		h, aerr := p.Auth(ctx)
+		if aerr != nil {
+			return fmt.Errorf("%w: %v", ErrUnavailable, aerr)
+		}
+		if h != "" {
+			req.Header.Set("Authorization", h)
+		}
+	}
+	resp, err := p.Client.Do(req)
+	if err != nil {
+		return fmt.Errorf("%w: %v", ErrUnavailable, err)
+	}
+	defer func() { _ = resp.Body.Close() }()
+
+	switch {
+	case resp.StatusCode == http.StatusConflict:
+		// Already provisioned. The product's insert is idempotent on the
+		// primary key, so this is success from our point of view.
+		return nil
+	case resp.StatusCode/100 == 2:
+		return nil
+	default:
+		b, _ := io.ReadAll(io.LimitReader(resp.Body, 512))
+		return fmt.Errorf("%w: %d %s", ErrUnavailable, resp.StatusCode, b)
+	}
+}