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`.

coderd/database/types.go

@@ -67,9 +67,10 @@ func (t *TemplateACL) Scan(src interface{}) error {
 	switch v := src.(type) {
 	case string:
 		return json.Unmarshal([]byte(v), &t)
-	case []byte, json.RawMessage:
-		//nolint
-		return json.Unmarshal(v.([]byte), &t)
+	case []byte:
+		return json.Unmarshal(v, &t)
+	case json.RawMessage:
+		return json.Unmarshal(v, &t)
 	}
 
 	return xerrors.Errorf("unexpected type %T", src)
@@ -85,9 +86,10 @@ func (t *WorkspaceACL) Scan(src interface{}) error {
 	switch v := src.(type) {
 	case string:
 		return json.Unmarshal([]byte(v), &t)
-	case []byte, json.RawMessage:
-		//nolint
-		return json.Unmarshal(v.([]byte), &t)
+	case []byte:
+		return json.Unmarshal(v, &t)
+	case json.RawMessage:
+		return json.Unmarshal(v, &t)
 	}
 
 	return xerrors.Errorf("unexpected type %T", src)
@@ -112,6 +114,27 @@ type WorkspaceACLEntry struct {
 	Permissions []policy.Action `json:"permissions"`
 }
 
+// WorkspaceACLDisplayInfo supplements workspace ACLs with the actors'
+// display info.  Key is string rather than uuid.UUID as this aligns
+// with how RBAC represents actor IDs.
+type WorkspaceACLDisplayInfo map[string]struct {
+	Name      string `json:"name"`
+	AvatarURL string `json:"avatar_url"`
+}
+
+// WorkspaceACLDisplayInfo is only used to read from the DB.
+func (w *WorkspaceACLDisplayInfo) Scan(src interface{}) error {
+	switch v := src.(type) {
+	case string:
+		return json.Unmarshal([]byte(v), w)
+	case []byte:
+		return json.Unmarshal(v, w)
+	case json.RawMessage:
+		return json.Unmarshal(v, w)
+	}
+	return xerrors.Errorf("unexpected type %T", src)
+}
+
 type ExternalAuthProvider struct {
 	ID       string `json:"id"`
 	Optional bool   `json:"optional,omitempty"`