v0.4.0

Implementation Changes

• Retry DEADLINE_EXCEEDED (via synth). (#7920)
• Remove classifier for Python 3.4 for end-of-life. (#7535)

New Features

• Add DatasourceServiceClient (via synth). (#8630)
• Add start_manual_transfer_runs method (via synth). (#8630)
• Add client_info/version_info support (via synth). (#8630)
• Allow passing kwargs to create_channel (via synth). (#8630)
• Add path helpers (via synth). (#8630)
• Add protos as an artifact to library (#7205)

Documentation

• Add compatibility check badges to READMEs. (#8288)
• Adjust indentation on scheduled query sample. (#8493)
• Add docs job to publish to googleapis.dev. (#8464)
• Add sample to schedule query with BQ DTS. (#7703)
• Add nox session docs (via synth). (#7765)
• Updated client library documentation URLs. (#7307)
• Pick up stub docstring fix in GAPIC generator. (#6965)

Internal / Testing Changes

• Blacken noxfile.py, setup.py (via synth). (#8116)
• Add empty lines (via synth). (#8050)
• Remove unused message exports (via synth). (#7263)
• Protoc-generated serialization update. (#7075)