add constraints file

Author: parthea

gapic/templates/testing/constraints-3.14.txt.j2

@@ -0,0 +1,20 @@
+{% from '_pypi_packages.j2' import pypi_packages %}
+# We use the constraints file for the latest Python version
+# (currently this file) to check that the latest
+# major versions of dependencies are supported in setup.py.
+# List all library dependencies and extras in this file.
+# Require the latest major version be installed for each dependency.
+# e.g., if setup.py has "google-cloud-foo >= 1.14.0, < 2.0.0",
+# Then this file should have google-cloud-foo>=1
+google-api-core>=2
+google-auth>=2
+proto-plus>=1
+protobuf>=6
+{% for package_tuple, package_info in pypi_packages.items() %}
+{# Quick check to make sure `package_info.package_name` is not the package being generated so we don't circularly include this package in its own constraints file. #}
+{% if api.naming.warehouse_package_name != package_info.package_name %}
+{% if api.requires_package(package_tuple) %}
+{{ package_info.package_name }}>={{ (package_info.upper_bound.split(".")[0] | int) - 1 }}
+{% endif %}
+{% endif %}
+{% endfor %}