Feature Request: Support Custom Clouds

[bblommers]

We have a custom cloud registered like so:

az cloud register --name OurCloud ..

We'd like to use it in conjunction with the azure-webapp-maven-plugin, configured like so:

<plugin>
    <groupId>com.microsoft.azure</groupId>
    <artifactId>azure-webapp-maven-plugin</artifactId>
    <version>2.14.1</version>
    <configuration>
        <auth>
	        <type>azure_cli</type>
        </auth>
        ...                             

But this throws an IllegalArgumentException when calling mvn azure-webapp:deploy:

...
Caused by: java.lang.IllegalArgumentException: Unknown azure environment.
    at com.microsoft.azure.toolkit.lib.auth.AzureEnvironmentUtils.getCloudName (AzureEnvironmentUtils.java:44)
    at com.microsoft.azure.toolkit.lib.auth.cli.AzureCliAccount.setupAfterLogin (AzureCliAccount.java:74)
    at com.microsoft.azure.toolkit.lib.auth.Account.login (Account.java:99)
    at com.microsoft.azure.toolkit.lib.auth.AzureAccount.login (AzureAccount.java:127)
...

The AzureEnvironmentUtils only supports the default clouds: Azure, China, Germany, USGov:

azure-maven-plugins/azure-toolkit-libs/azure-toolkit-auth-lib/src/main/java/com/microsoft/azure/toolkit/lib/auth/AzureEnvironmentUtils.java

Lines 22 to 31 in f173242

	static {
	// the first alias is the cloud name in azure cli
	// the second alias is the display name, all other aliases are only used in our toolkit
	putAliasMap(AzureEnvironment.AZURE, "AzureCloud", "azure", "azure_cloud", "GLOBAL");
	putAliasMap(AzureEnvironment.AZURE_CHINA, "AzureChinaCloud", "azure_china", "AzureChina", "azure_china_cloud", "CHINA");
	// the TYPO:azure_german comes from azure cli: https://docs.microsoft.com/en-us/azure/germany/germany-get-started-connect-with-cli
	putAliasMap(AzureEnvironment.AZURE_GERMANY, "AzureGermanCloud", "azure_germany", "azure_german",
	"azure_germany_cloud", "azure_german_cloud", "AzureGerman", "AzureGermany", "GERMAN");
	putAliasMap(AzureEnvironment.AZURE_US_GOVERNMENT, "AzureUSGovernment", "azure_us_government", "US_GOVERNMENT");
	}

Considering that we're logging in using the az CLI, I don't see why the exact cloud name matters - az has already validated that this cloud exists/is valid.