RESTBase already stores information about the namespace of a page. The next step is to provide this listing to the public via the following API endpoints:
- `/{domain}/v1/page/namespace/`: lists all of the available namespaces, including aliases (if any), and perhaps canonical names as well
- `/{domain}/v1/page/namespace/{namespace}`: gets info about a namespace, such as ID, name, aliases, canonical names, etc.
- `/{domain}/v1/page/namespace/{namespace}/`: lists all of the pages available in storage that belong to the namespace with the given name; note that `{namespace}` may refer to a namespace's ID, name or alias
This should be easily-achievable. Specifically, it warrants the creation of a second table, which would store information about namespaces. Then, linking it to the table of pages titles (via the `namespace` property and the `by_ns` secondary index) should give us the list of pages in the given namespace.