chore: sync to master#616

Merged

gcf-merge-on-green[bot] merged 11 commits intogoogleapis:byoidfrom

bojeil-google:sync-to-master

Sep 29, 2020

Commits on Sep 2, 2020

refactor: split 'with_quota_project' into separate base class (#561)

busunkim96
and
tseaver
authored

Commits on Sep 3, 2020

Commits on Sep 8, 2020

fix: migrate signBlob to iamcredentials.googleapis.com (#600)
busunkim96
authored

Commits on Sep 16, 2020

chore: release 1.21.2 (#601)
release-please[bot]
authored

Commits on Sep 17, 2020

fix: fix expiry for `to_json()` (#589)
wescpy
authored

Commits on Sep 22, 2020

chore: add default CODEOWNERS (#609)
busunkim96
authored

Commits on Sep 23, 2020

chore: release 1.21.3 (#607)
release-please[bot]
authored

Commits on Sep 28, 2020

Commits on Sep 29, 2020

Merge remote-tracking branch 'upstream/byoid'
bojeil-google
committed