v0.21.0 Release

NOTICE: This repo will soon contain the code for all the other related google-cloud-cpp-* repos. As a new monorepo (#3612), the versioning of this repo will be changing to have a single per-repo version. The per-library version numbers will be removed in favor of the repo version. See #3615 for more info.

Storage Changes

BREAKING CHANGES

• fix!: moved IAM-related symbols to the correct inlined namespace (#3453)
  Most users should not notice any difference, but those that explicitly referenced
  symbols through the google::cloud::storage::v0 namespace may need to switch
  to google::cloud::storage (the recommended approach) or
  google::cloud::storage::v1. We apologize if this causes you inconvenience.

Other Changes:

• feat: add support for iam conditions (#3497)
• bug: express libcurl version in hex (#3487)
• bug: check curl connection before unpausing (#3485)
• feat: allow domain named buckets in signed URLs v4 (#3463)
• feat: implement virtual hostname V4 signatures
• feat: add configuration options to set the SSL root of trust (#3455)
• doc: add doxygen comments for ParallelUploadFile (#3448)
• feat: support x-goog-content-sha256 for V4 signed URLs (#3435)

Bigtable Changes

BREAKING CHANGES

• fix!: moved IAM-related symbols to the correct inlined namespace (#3453)
  Most users should not notice any difference, but those that explicitly referenced
  symbols through the google::cloud::bigtable::v0 namespace may need to switch
  to google::cloud::bigtable (the recommended approach) or
  google::cloud::bigtable::v1. We apologize if this causes you inconvenience.

Other Changes

• None