feat(shared): add CreateOrg, RollbackOrg and CreateUser

Adopts sitesvc's retry-on-duplicate-key slug loop. The control plane
previously returned an error when it lost the slug race.

shared/provision/user.go

@@ -0,0 +1,65 @@
+package provision
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/mrhid6/vantage/shared/models"
+	"go.mongodb.org/mongo-driver/v2/mongo"
+	"golang.org/x/crypto/bcrypt"
+)
+
+// BcryptCost is the work factor for every password hash Vantage writes.
+// Changing it changes nothing about existing hashes, which carry their own cost.
+const BcryptCost = 12
+
+// ErrEmailTaken is returned when the unique index on users.email rejects an insert.
+var ErrEmailTaken = errors.New("email already registered")
+
+// CreateUser hashes password and inserts the user. An empty password leaves the
+// hash empty, which is how OIDC users are stored.
+func CreateUser(ctx context.Context, db *mongo.Database, orgID, email, password, role, authSource string) (*models.User, error) {
+	var hash string
+	if password != "" {
+		b, err := bcrypt.GenerateFromPassword([]byte(password), BcryptCost)
+		if err != nil {
+			return nil, err
+		}
+		hash = string(b)
+	}
+	return CreateUserWithHash(ctx, db, orgID, email, hash, role, authSource)
+}
+
+// CreateUserWithHash inserts a user whose password was already hashed
+// elsewhere. sitesvc hashes at signup and only holds the hash by the time the
+// verification link is opened.
+func CreateUserWithHash(ctx context.Context, db *mongo.Database, orgID, email, passwordHash, role, authSource string) (*models.User, error) {
+	email = strings.ToLower(strings.TrimSpace(email))
+	if email == "" {
+		return nil, fmt.Errorf("email required")
+	}
+	if !models.ValidRole(role) {
+		return nil, fmt.Errorf("invalid role %q", role)
+	}
+
+	u := &models.User{
+		UserID:       uuid.NewString(),
+		OrgID:        orgID,
+		Email:        email,
+		PasswordHash: passwordHash,
+		Role:         role,
+		AuthSource:   authSource,
+		CreatedAt:    time.Now().UTC(),
+	}
+	if _, err := db.Collection("users").InsertOne(ctx, u); err != nil {
+		if mongo.IsDuplicateKeyError(err) {
+			return nil, ErrEmailTaken
+		}
+		return nil, err
+	}
+	return u, nil
+}