Bigtable

• Exists method added (#3769)
• Bigtable: non-functional improvements relating to error handling (#3809)
• bigtable: updated_documentation (#3833)

Pub/Sub

• pubsub: remove TODO (#3845)
• Pubsub: Set default maxInboundMessageSize to 20MB (#3844)
• setMaxInboundMessageSize in Pubsub exmaple (#3825)
• pubsub: reject expired and duplicate messages (#3743)
• Re-generate library using google-cloud-clients/google-cloud-pubsub/synth.py (#3824)

Storage

• WIP: Storage: Deprecate DeleteRules and add LifecycleRules to accommodate SetStorageClass actions (#3795)
• Add assumptions to storage integration tests (#3813)

Dependencies

• Grpc (#3733)

Documentation

• Fix [cloud-nio] link (#3835) - docs: Update javadoc for network client (#3832)
• Fix container analysis link (#3814)
• Add android note (#3631)

Internal / Testing Changes

• Add codecov (#3842)
• Bumping gax, using gax-bom (#3841)
• Add compute synth (#3830)
• Update CODEOWNERS. (#3831)
• Make testDownloadPublicBlobWithoutAuthentication skippable with an environment variable (#3828)
• Bump next snapshot (#3810)
• Add issue/pr templates (#3794)
• Add Kokoro release scripts (#3818)