feat: add sharing info to /workspaces endpoint (#21049)

closes: https://github.com/coder/internal/issues/858

Similar to https://github.com/coder/coder/pull/19375, this one uses
system permissions for fetching actual user and group data.

Modifies the `workspaces_expanded` view to fetch the required data; this way it's made available to all code paths that make use of it.  

Also fixes a bug in a test helper function that can result in `null` being saved to the DB for `user_acl` or `group_acl` and break tests; a defensive check constraint that prevents this is worth a PR, e.g:

`ALTER TABLE workspaces
   ADD CONSTRAINT group_acl_is_object CHECK (jsonb_typeof(group_acl) = 'object');`

Also adds missing  `OwnerName` in `ConvertWorkspaceRows`.

codersdk/workspaces.go

@@ -73,7 +73,8 @@ type Workspace struct {
 	// and IsPrebuild returns false.
 	IsPrebuild bool `json:"is_prebuild"`
 	// TaskID, if set, indicates that the workspace is relevant to the given codersdk.Task.
-	TaskID uuid.NullUUID `json:"task_id,omitempty"`
+	TaskID     uuid.NullUUID          `json:"task_id,omitempty"`
+	SharedWith []SharedWorkspaceActor `json:"shared_with,omitempty"`
 }
 
 func (w Workspace) FullName() string {
@@ -695,6 +696,14 @@ type WorkspaceUser struct {
 	Role WorkspaceRole `json:"role" enums:"admin,use"`
 }
 
+type SharedWorkspaceActor struct {
+	ID        uuid.UUID                `json:"id" format:"uuid"`
+	ActorType SharedWorkspaceActorType `json:"actor_type" enums:"group,user"`
+	Name      string                   `json:"name"`
+	AvatarURL string                   `json:"avatar_url,omitempty" format:"uri"`
+	Roles     []WorkspaceRole          `json:"roles"`
+}
+
 type WorkspaceRole string
 
 const (
@@ -703,6 +712,13 @@ const (
 	WorkspaceRoleDeleted WorkspaceRole = ""
 )
 
+type SharedWorkspaceActorType string
+
+const (
+	SharedWorkspaceActorTypeGroup SharedWorkspaceActorType = "group"
+	SharedWorkspaceActorTypeUser  SharedWorkspaceActorType = "user"
+)
+
 func (c *Client) WorkspaceACL(ctx context.Context, workspaceID uuid.UUID) (WorkspaceACL, error) {
 	res, err := c.Request(ctx, http.MethodGet, fmt.Sprintf("/api/v2/workspaces/%s/acl", workspaceID), nil)
 	if err != nil {