Persisted indices
This pull request implements the feature of persisted indices, allowing users to save an index and load it later using an ID. The implementation follows the official LlamaIndex documentation. The directory for storing the indices is set to /indices/.
Users can set the ID for the index in the local files tab, as shown in the screenshot below:
An index can be loaded by entering its ID. When the index exists, it is not required to upload a file. If files are updated while a persisted index is configured, the files are automatically appended to the index. Currently, there is no functionality to remove files from the index.
One thing I am not sure about: should the persisted_index_id be place on the settings page?