Add public convenience string constants for endpoints of each cloud (sovereign and public)

[henrik-me]

Context
Customers have had difficulty finding the right documentation pages:
https://docs.microsoft.com/en-us/azure/azure-government/documentation-government-developer-guide#endpoint-mapping
https://docs.microsoft.com/en-us/azure/china/resources-developer-guide#check-endpoints-in-azure

See also other libraries exposing these:

• obj-c
• .net

Reference:
https://identitydivision.visualstudio.com/Engineering/_workitems/edit/1063014

Other:
AzureAD/microsoft-authentication-library-for-java#258

[rayluo]

See also other libraries exposing these:

• obj-c
• .net

OK. After comparison, we think the .net naming matches this AAD national cloud document closely. We will adopt it.

[jmehnle]

Any plans to implement this?

[rayluo]

Any plans to implement this?

Hi @jmehnle , a new usage pattern is documented in our doc staging site (please search the keyword "authority (str)") in this page. It will be included in our late Nov release.

[jmehnle]

That seems like a great solution. Thanks, @rayluo and team! Looking forward to that late-November release.