Version 0.28.0

Changed

• pygls 0.10.0. This version explicitly uses pydantic and better supports initialization options. This enables use to remove the cached-property dependency for Python versions 3.6 and 3.7.
• pydantic is now used for initialization options parsing. Simplified so much that we were able to remove initializationOption-specific tests.
• Explicitly add method for did_open, for some weird reason the latest pygls bugs out if you don't explicitly set this function to at least an empty function.

Removed

• Support for Python 3.6.0. We now only support Python 3.6.1+.
• Monkeypatch for null versus missing attributes. pydantic / pygls>=0.10.0 handles this.