Add google-auth as a direct dependency, and ensure that the minimum supported version is tested

[parthea]

google-auth is used in this repository but it is not explicitly listed as a direct dependency in setup.py

google-auth should be added as a direct dependency here:

python-aiplatform/setup.py

Lines 174 to 184 in 9a19545

	install_requires=(
	"google-api-core[grpc] >= 1.32.0, <3.0.0dev,!=2.0.*,!=2.1.*,!=2.2.*,!=2.3.*,!=2.4.*,!=2.5.*,!=2.6.*,!=2.7.*",
	"proto-plus >= 1.22.0, <2.0.0dev",
	"protobuf>=3.19.5,<5.0.0dev,!=3.20.0,!=3.20.1,!=4.21.0,!=4.21.1,!=4.21.2,!=4.21.3,!=4.21.4,!=4.21.5",
	"packaging >= 14.3",
	"google-cloud-storage >= 1.32.0, < 3.0.0dev",
	"google-cloud-bigquery >= 1.15.0, < 4.0.0dev",
	"google-cloud-resource-manager >= 1.3.3, < 3.0.0dev",
	"shapely < 3.0.0dev",
	"setuptools; python_version >= '3.12'",
	),

The minimum supported version of google-auth should also be added to testing/constraints-3.7.txt so that we run tests against it.

python-aiplatform/testing/constraints-3.7.txt

Lines 1 to 14 in 9a19545

	# This constraints file is used to check that lower bounds
	# are correct in setup.py
	# List *all* library dependencies and extras in this file.
	# Pin the version to the lower bound.
	#
	# e.g., if setup.py has "foo >= 1.14.0, < 2.0.0dev",
	# Then this file should have foo==1.14.0
	google-api-core==1.32.0
	proto-plus==1.22.0
	protobuf==3.19.6
	mock==4.0.2
	google-cloud-storage==2.0.0
	packaging==20.0 # Increased for compatibility with MLFlow
	grpcio-testing==1.34.0

See related issue googleapis/gapic-generator-python#1922