Lexicon v3.15.0

Added

• Add pyotp Python dependency in Lexicon to help implementing OTP (one-time password)
  on providers whose API supports this kind of authentication.
• Add OTP support on hover provider, with a new flag named --auth-totp-secret.
• Add type marker py.typed to inform types checkers about availability of type
  annotations in Lexicon codebase.

Modified

• Fix and modernize ReadTheDoc documentation build.
• Better error management and resource cleanup when Client is used as a context manager.

Removed

• Stop using cryptography in providers where only hashing is needed.