v0.17.0

Major updates:

• Initialize a server with the MongoDB backend with entries from a JSON file (#220).
• Use the latest MongoDB v4 (v4.4) for tests and in docker-compose files (#220).

Developer updates:

• Dependencies updated:
  • optimade (v0.13.3), which uses the latest pydantic (v1.8) version.
  • pymatgen (v2021.3) using semantic versioning to stay in v2021.