fix: use definite assignment assertion operator

We used declare which is the wrong use-case for this. See: https://www.typescriptlang.org/docs/handbook/2/classes.html#--strictpropertyinitialization

src/models/namespace.ts

@@ -18,14 +18,14 @@ export interface INamespace extends AbstractModel {
 }
 
 export default class NamespaceModel extends AbstractModel implements INamespace {
-	declare id: number
-	declare title: string
-	declare description: string
+	id!: number
+	title!: string
+	description!: string
 	owner: IUser
 	lists: IList[]
-	declare isArchived: boolean
-	declare hexColor: string
-	declare subscription: ISubscription
+	isArchived!: boolean
+	hexColor!: string
+	subscription!: ISubscription
 
 	created: Date
 	updated: Date