Sharing backend: shares CRUD + ACL enforcement everywhere (#16)

Co-authored-by: Steve Dudenhoeffer <[email protected]>

internal/domain/domain.go

@@ -21,6 +21,17 @@ var (
 	// reference it (the FK is ON DELETE RESTRICT). Mapped to 409.
 	ErrPlantInUse = errors.New("plant is referenced by plantings")
 
+	// ErrShareUserNotFound means no account exists for the email a share invite
+	// targeted (v1 shares an existing user only — no invitation emails). Mapped to
+	// 404 with a clear "no account with that email" message.
+	ErrShareUserNotFound = errors.New("no account with that email")
+	// ErrCannotShareWithSelf means the owner tried to share a garden with their
+	// own account. Mapped to 400.
+	ErrCannotShareWithSelf = errors.New("cannot share a garden with yourself")
+	// ErrShareExists means the garden is already shared with that user. Mapped to
+	// 409 (change the existing share's role instead).
+	ErrShareExists = errors.New("garden already shared with that user")
+
 	// ErrInvalidInput means the caller supplied structurally invalid data (empty
 	// required field, malformed value). Mapped to 400.
 	ErrInvalidInput = errors.New("invalid input")
@@ -60,6 +71,9 @@ const (
 
 	RoleViewer = "viewer"
 	RoleEditor = "editor"
+	// RoleOwner is not a garden_shares row (ownership is implicit via
+	// gardens.owner_id); it's the value Garden.MyRole carries for an owner.
+	RoleOwner = "owner"
 
 	KindBed       = "bed"
 	KindGrowBag   = "grow_bag"
@@ -116,6 +130,10 @@ type Garden struct {
 	Version   int64   `json:"version"`
 	CreatedAt string  `json:"createdAt"`
 	UpdatedAt string  `json:"updatedAt"`
+
+	// MyRole is the requesting actor's effective role on this garden ("owner",
+	// "editor", or "viewer"). Computed by the service, never persisted.
+	MyRole string `json:"myRole,omitempty"`
 }
 
 // GardenShare grants a non-owner user viewer or editor access to a garden.
@@ -130,6 +148,14 @@ type GardenShare struct {
 	UpdatedAt string `json:"updatedAt"`
 }
 
+// ShareWithUser is a garden share plus the target user's identity, for the
+// sharing UI's list (which shows who a garden is shared with).
+type ShareWithUser struct {
+	GardenShare
+	Email       string `json:"email"`
+	DisplayName string `json:"displayName"`
+}
+
 // GardenObject is any placeable object in a garden (bed, container, tree, path…).
 // Positioned by center point + rotation about center, in garden space.
 type GardenObject struct {