[AutoPR network/resource-manager] Add ExpressRoute gateway resource

[AutorestCI]

Created to sync Azure/azure-rest-api-specs#3776

[AutorestCI]

(message created by the CI based on PR content)

Installation instruction

Package azure-mgmt-network

You can install the package azure-mgmt-network of this PR using the following command:
pip install "git+https://github.com/Azure/azure-sdk-for-python@restapi_auto_3776#egg=azure-mgmt-network&subdirectory=azure-mgmt-network"

You can build a wheel to distribute for test using the following command:
pip wheel --no-deps "git+https://github.com/Azure/azure-sdk-for-python@restapi_auto_3776#egg=azure-mgmt-network&subdirectory=azure-mgmt-network"

If you have a local clone of this repository, you can also do:

• git checkout restapi_auto_3776
• pip install -e ./azure-mgmt-network

Or build a wheel file to distribute for testing:

• git checkout restapi_auto_3776
• pip wheel --no-deps ./azure-mgmt-network

Direct download

Your files can be directly downloaded here:

• azure-mgmt-network-2.1.0.zip
• azure_mgmt_network-2.1.0-py2.py3-none-any.whl