Major features
* **Add support for SPARQL [INSERT DATA](https://www.w3.org/TR/2013/REC-sparql11-update-20130321/#insertData) and [DELETE DATA](https://www.w3.org/TR/2013/REC-sparql11-update-20130321/#deleteData) queries**.
* They are sent to the server using the SPARQL 1.1 protocol and must completely run inside a quantum.
* Quads that could be processed inside the quantum will be ignored.
* Upon query completion, the SaGe server returns the set of quads that were successfully processed during the quantum. Quads that could not be processed due to an error are ignored, to avoid a crash of query execution.
* **Add support for [PostgreSQL](https://www.postgresql.org/) as a backend**. Two backends are available: `postgres` and `postgres-mvcc`, where the later rely on multi-version concurrency control to provide reads against consistent snapshots of the RDF graphs. More details on these backends are available in the technical documentation.
* **All HTTP interfaces have been unified under the [SPARQL 1.1 protocol](https://www.w3.org/TR/2013/REC-sparql11-protocol-20130321/)**. Consequently, all previous APIs have been deprecated.
* The HTTP server has been rewritten using [FastAPI](https://fastapi.tiangolo.com/) and [Uvicorn](https://www.uvicorn.org/). This new version provides cleaner errors when the API is misused and **significantly increase performance under heavy load**.
* **The SaGe Web interface has been externalized as a standalone project** called [`sage-web`](https://github.com/sage-org/sage-web). Consequently, it is no longer included with `sage-engine` and must be used separately.
* **A complete technical documentation is available** in the `docs` directory and can be built using [sphinx](http://www.sphinx-doc.org/en/master/). It describes the `sage-engine` software, how to use it, how to configure each backend and includes the complete autodoc of the `sage` package. Upon merge, this doc will be hosted on the Github page of this repo.
Minor features
* Update the syntax of YAML config files.
* The `datasets` field has been renamed to `graphs`. This change is part of a general effort to align the vocabulary used inside the package with the RDF and SPARQL specifications.
* Added the `stateless` field to switch the server between stateless and stateful mode.
* The `quota` and `max_results` can now be set to `"inf"` to use an infinite quantum and disable the limit of results sent per HTTP request, respectively. Doing so will trigger warning messages when starting the server, but it's fine if you know what you are doing 😉
* Support for RDF config files, but it is currently reserved for advanced usage of the engine.
* Increase test coverage.
* Add [type hints](https://docs.python.org/3/library/typing.html) to all functions, methods & classes in the `sage` package.
* Complete rewriting of the pydoc of all functions, methods & classes in the `sage` package.